HK1162221B - System and method for controlling power balance in an electrical/mechanical system - Google Patents

Description

System and method for controlling power balance in electrical/mechanical system

Technical Field

This specification describes an electrical/mechanical system having at least a three-point power interface.

Background

Referring to fig. 1 and 2, an example of such a system includes one or more linear actuator systems 10 powered by alternating current power from an amplifier 34, the amplifier 34 being powered by a Direct Current (DC) power source, such as a battery 11. As described in more detail below, the actuator system 10 includes a stator having a set of coil windings and a rod. The rod may be a plunger with a set of permanent magnets. The control system defines a current pattern to be applied to the coil windings to define a magnetic flux density across a gap between the coil windings and a series of magnets on the rod to generate a force to move the rod of the magnet linear actuator for movement. The movement of the rod relative to the coil defines the actuator mechanical power, which is shown at 2. The power applied by the battery 11 to the coils through the DC bus 13 is shown at 4, while the dissipated power (including power dissipated in the coils, core losses in the motor, and power electronics losses in the amplifier) is shown at 6. The power flows 2, 4 and 6 define a three-point power interface between the actuator system 10 and the world outside the actuator.

It will be appreciated that the sum of the power across the three-point power interface must be zero, i.e. the power flowing into the actuator system must be balanced with the power flowing out. As shown in fig. 2 and described in more detail below, the dissipated power 6 always flows out of the actuator system, while each of the actuator mechanical power 2 and the DC bus power 4 may flow into or out of the actuator system. If a mechanical event occurs that causes the power flow into the actuator to be greater than the dissipated power out of the actuator system, then DC bus power 4 will flow out of the actuator system onto the DC bus. This is referred to herein as a regeneration event. It will be appreciated that regeneration may have the effect of applying current back to the battery 11 and thereby recharging the battery 11, but if the regeneration current is high enough, regeneration may damage the battery.

Disclosure of Invention

In one embodiment of a method of controlling a commutating actuator having a stator, a rod, a plurality of magnets and at least one coil, the rod being movable relative to the stator at an interface between the stator and the rod, the plurality of magnets being movable with the rod and disposed relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface, the at least one coil being defined on the stator relative to the interface such that a current applied to the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to variations in the current, a first input and a second input are received. In response to the first input, the second magnetic flux is controlled such that the second magnetic flux has a predetermined phase with respect to the first magnetic flux. In response to the second input, and variably with respect to the first input, the second magnetic flux is controlled such that the phase of the second magnetic flux with respect to the first magnetic flux is displaced from a predetermined phase.

In another embodiment of a method of controlling a commutating actuator having a stator, a rod, a plurality of magnets, at least one coil, and a battery, the battery having a voltage, the rod being movable relative to the stator at an interface between the stator and the rod, the plurality of magnets being movable with the rod and disposed relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface, the at least one coil being disposed on the stator relative to the interface such that a current applied to the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to a change in current, the battery having a voltage. The relative position between the rod and the stator is determined. First and second inputs are received. The variable level is controlled in response to the relative position and the first input to provide a q-axis component of the current on the at least one coil relative to the first magnetic flux and the second magnetic flux. The variable level is controlled in response to a second input to provide a d-axis component of current on the at least one coil relative to the first and second magnetic fluxes.

In another embodiment, an electrically commutated actuator and control system includes a stator and a rod movable relative to the stator at an interface between the stator and the rod. A plurality of magnets are movable with the rod. The plurality of magnets are arranged relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface. At least one coil is disposed on the stator relative to the interface such that a current on the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to a change in the current. The variable amplifier applies a varying current across the at least one coil, the current including a q-axis component with respect to the first and second magnetic fluxes and a d-axis component with respect to the first and second magnetic fluxes. The control circuit defines a q-axis component in response to the first input and variably defines a d-axis component relative to the q-axis component in response to the second input.

In yet another embodiment, an apparatus and control system in a vehicle for actively suspending an apparatus in the vehicle includes an apparatus that changes position relative to the vehicle in response to a force applied to or by the vehicle. The electrically commutated actuator comprises a stator and a rod, the rod being movable with the stator at an interface between the stator and the rod. A plurality of magnets are movable with the rod. The plurality of magnets are disposed relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface. At least one coil is disposed on the stator relative to the interface such that a current on the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to variations in the current. The rod is in mechanical communication with the device such that a force is applied between the device and the at least one coil through the rod. The variable amplifier applies a varying current across the at least one coil, the current including a q-axis component with respect to the first and second magnetic fluxes and a d-axis component with respect to the first and second magnetic fluxes. The control circuit defines a q-axis component in response to the first input and variably defines a d-axis component relative to the q-axis component in response to the second input.

Drawings

A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the following figures, in which:

FIG. 1 is a schematic view of a prior art suspension actuator system;

FIG. 2 is a schematic power flow diagram of a prior art suspension actuator system;

FIG. 3 is a schematic block diagram illustrating an actuator system in accordance with one embodiment of the present invention;

FIG. 4 is a waveform illustrating the magnetic flux density exhibited by the system shown in FIG. 3;

FIG. 5 is a waveform of the magnetic flux density exhibited by the system of FIG. 3;

FIG. 6 is a graphical representation of a phase force constant that may be applied to the system shown in FIG. 3;

FIG. 7 is a phase diagram for an actuator circuit;

FIG. 8 is a phase diagram for an actuator circuit;

FIG. 9 is a phase diagram of an actuator circuit for use in the system according to FIG. 3;

FIG. 10 is a functional block diagram of steps affected by the system shown in FIG. 3; and

fig. 11 is a functional block diagram of steps affected by the system shown in fig. 3.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.

Detailed Description

With specific reference to certain embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as fall within the scope of the present disclosure, including the appended claims.

While the embodiments presented in this specification are described in the context of a linear actuator, it should be understood that this is for exemplary purposes only, and one skilled in the art will appreciate in light of this disclosure that the systems and methods described herein may be implemented using other electrical/mechanical devices and arrangements. Thus, for example, although the actuators discussed herein are linear actuators and the rods are linear plungers, it should be understood that the actuators may be rotary motors and the rods may be rotatable or may implement a nut/threaded screw action in response to force rather than direct linear movement. Referring to fig. 3, the linear actuator 10 may include a stator 16 and a rod, which in this embodiment is a plunger 12 that is linearly movable reciprocally in an axial direction 14 relative to the stator 16. The arrow 14 is shown in bold in fig. 3 (as well as in fig. 1) to indicate a direct mechanical connection, in this case for example between the plunger 12 and the vehicle suspension 15, so that the plunger 12 and the vehicle suspension 15 can move together in the reciprocating direction shown at 14. The stator 16 may be secured to an actuator housing (not shown) that surrounds the plunger and stator and is secured to a vehicle chassis 25, interposed between the actuator and the vehicle chassis as shown in bold in fig. 3 (and in fig. 1). As described below, the plunger 12 and stator 16 may be arranged in a two-pole configuration, although it should be understood that this is for illustrative purposes only, and that four-pole arrangements and higher order arrangements may be employed. The plunger 12 may include a non-magnetic rod 18 and an axially magnetized cylindrical permanent magnet 20, the permanent magnet 20 being fixed around the plunger and alternating in polarity in the direction 14, resulting in the generation of magnetic flux lines 22. The plunger may also include cylindrical pole pieces 24 located between the magnets. In another embodiment, the actuator is a double-sided linear motor and the plunger comprises rectangular pole pieces 24 and rectangular permanent magnets 20 magnetized such that the air gap flux density is perpendicular to the line defined by the air gap. While a moving magnet linear actuator is described in the present embodiment, it is to be understood that this is for exemplary purposes only and that one skilled in the art, in light of the present disclosure, will appreciate that the systems and methods described herein can be implemented using an actuator having a stator with at least one coil attached thereto and a rod with at least one permanent magnet attached thereto, the stator and rod moving relative to each other in a linear or rotational manner (moving the coil or moving the magnet). While a three-phase actuator is described in the present embodiment, it will be appreciated by those skilled in the art in light of the present disclosure that the systems and methods described herein may be implemented with a different number of actuator phases (e.g., two-phase, four-phase, etc.).

The stator 16 may include a pair of non-magnetic cylindrical races 26 and a three-phase winding of 6 coils 28a, 30a, 32a, 28b, 30b and 32 b. It should be well understood that the coils in each pair of windings 28a/28b, 30a/30b, 32a/32b may be wound and electrically connected to each other to increase the magnetic flux between the two coils generated by the two coils in response to Alternating Current (AC) current delivered to the coils from the inverter 34 through the respective wire 28c, 30c, or 32 c. Inverter 34 may take three AC current signals from DC power source 11 via DC bus 13, each of which is 120 ° out of electrical phase with each of the other two signals, and apply the signals to conductors 28c, 30c, and 32c, respectively. More specifically, in the illustrated embodiment, if the stator is activated to move the plunger 12 to the right (in the view shown in FIG. 3), the signal on line 30c lags the signal on line 28c by 120, while the signal on line 32c lags the signal on line 30c by 120, whereas if the stator coil is activated to move the plunger 12 to the left, the signal on line 30c leads the signal on line 28c by 120, while the signal on line 32c leads the signal on line 30c by 120.

Fig. 4 illustrates the air gap flux density contributed by the permanent magnets of the plunger in the air gap between the stator and the plunger at a point aligned with a given point on the stator (e.g., at winding 28 a) when the plunger 12 is moved in either axial direction 14 relative to the stator. Point 35 in fig. 4 represents the air gap flux density of the stator winding 28a at its location shown in fig. 3. At 36, the plunger 12 moves in one of the directions 14 so that the winding 28a directly opposes the next occurring pole piece 24, while at 38, the plunger 12 continues its movement so that the winding 28a directly opposes the second occurring pole piece. Thus, the pole pitch of the permanent magnet on the plunger 12 is indicated at 40.

Figure 5 illustrates the air gap flux density contributed by the windings 28a in the air gap between the stator and the plunger at a point aligned with a given point of the plunger (e.g. at pole piece 24') when the plunger 12 is moved in the same axial direction as reflected by the flux density curve shown in figure 4. As described in more detail below, the system may include a linear encoder 62 and a control system 21, such that the linear encoder detects the position of the plunger 12 relative to the stator 16 and provides a relative position of the plunger relative to the control system 21 that determines the magnitude of the "d-axis" and "q-axis" components of the current signal through the wire 28c, or in another embodiment the magnitude and relative phase of the current signal (i.e., phase shift relative to the q-axis phase) caused by the varying voltage signal applied to the coil 28a by the inverter 34. As shown by comparison of fig. 4 and 5, the control system 21 can control the current signal on the coil 28a which produces an air gap flux density profile relative to the moving plunger 12 having the same sinusoidal waveform as the profile of fig. 4, but in this case with a 90 ° phase offset. It should be understood in the art that under ideal conditions a 90 phase offset current signal for coil 28a (and, thus, coil 28b as well) results in the magnetic force from coil 28a being most effectively applied to plunger 12 moving in direction 14. However, it should also be understood that the most effective phase shift in the coil current input to an actual motor/linear actuator may differ somewhat from 90 °. The method for calibrating the actuator coil current should be well understood and will not be described herein. It will therefore be appreciated that for any given permanent magnet actuator, whether a rotary electric machine or a linear actuator, there is a positional phase shift (between the curve defined by the air gap flux density contributed by the permanent magnet relative to the stator as the magnet and stator move relative to each other and the curve defined by the air gap flux density contributed by the stator coil relative to the permanent magnet during relative motion) that results in the most efficient application of force between the stator and magnet. The current applied to the actuator coil at such a phase (i.e., electrical phase) that produces such a phase shift (i.e., position phase) between the magnetic flux density curves is referred to as a "q-axis" current. For illustrative purposes only, an ideal situation is presented in fig. 4 and 5, and thus the exemplary position q-axis phase described herein is shown in fig. 5 with a 90 ° phase shift relative to fig. 4, but it should be understood that for a given actuator, the actual q-axis phase may differ from 90 ° in accordance with known principles and methods. It will be appreciated that the q-axis phase is typically defined for a given motor design, and consequently that rating for all subsequent motors of that type, even though the q-axis phase may be more precisely defined for a given individual motor. The present disclosure encompasses such methods of defining a q-axis phase.

Force (F) between the plunger 12 and the stator 16 caused by current flow in the coil_out) Given by the following formula:

F_outia (x), kfa (x) + ib (x), kfb (x) + ic (x) + kfc (x), wherein

ia (x): current signals on coils 28a and 28b

Kfa (x): phase force constant of windings 28a/28b

ib (x): current signals on coils 30a and 30b

Kfb (x): phase force constant of winding 30a/30b

ic (x): current signals on coils 32a and 32b

Kfc (x): phase force constant of winding 32a/32b

x: position of plunger 12 in axial direction 14 relative to stator 16

As explained above, each current signal ia (x), ib (x), and ic (x) is controlled such that the coil receiving the current signal (relative to the plunger) produces an air-gap flux density defining a curve having the same shape as the air-gap flux density curve defined by the permanent magnet of the plunger, which curve is observed as the plunger and stator move relative to each other, but which curve is phase shifted in phase by 90 ° relative to the permanent magnet flux curve (if in position q-axis phase in the ideal situation as described above). Since the coils and permanent magnets are arranged such that the respective air-gap flux curves viewed from the plunger by the pairs of coils 28a/28b, 30a/30b and 32a/32b are offset from each other by 120 °, the current signals ia (x), ib (x) and ic (x) are spaced 120 ° from each other in phase, with each current signal being offset by 120 ° from its respective air-gap flux curve from the plunger. As mentioned above, the air gap flux curve forms a sine wave, and the current signal ia (x) controlled on the coils 28a/28b can be described by the following equation:

ia (Ia) (2 × pi x (2 × mp) + phase _ shift), wherein

Ia: maximum amplitude of current ia (x)

x: relative position of plunger 12 in axial direction 14 with respect to coils 28a/28b

mp: magnetic or polar distance 40

phase _ shift: phase shift of the electrical q-axis phase relative to the q-axis phase at the location that results in the resulting air gap flux density curve (phase _ shift is 0 in the curve shown in fig. 5).

The control system defines 1a (either directly or by defining the magnitudes of the q-axis and d-axis current components) to apply a desired force to the plunger as described below. The formulae for ib (x) and ic (x) are similar to the ia (x) formulae and are therefore not described. Note that "x" is the relative position between the plunger and the corresponding coil. The relative position "x" may be considered as the axial distance between an arbitrarily selected point on the plunger and one of the aligned coils (i.e., x ═ 0) when the current ia (x) on coil pair 28a/28b is at the maximum on the curve, which describes the q-axis current when phase _ shift is 0. It should also be noted that the equation for the currents for the other two coils shifts the "2 x pi x/(2 x mp)" terms by 120 ° and 240 °, respectively, to describe the three-phase 120 shift in the current signal. For any relative position "x" between the plunger and the stator, the current functions ia (x), ib (x), and ic (x) define the currents that are correspondingly controlled on the corresponding coil pairs to apply the desired force. If the plunger and the stator are moved relative to each other, the current signal will vary according to their sinusoidal function, but if the plunger and the stator are fixed in position relative to each other, a constant current defined by the current function will be applied. The actual current function depends on the rectification scheme. For example, trapezoidal rectification will result in an actual current function that is different from an ideal sinusoidal function, and the sinusoidal function described herein is for illustrative purposes.

The phase force constant kfa (x) is determined by the magnet design of the actuator, and has units of newtons/ampere. The phase force constant is preferably a sine wave or similar, although the function may become more complex at high current levels. For normal current levels (i.e., when the actuator back iron is not heavily saturated, as should be well understood), and in the ideal case described above, the respective phase force constants of the coil pairs 28a/28b, 30a/30b and 32a/32b are defined by the following equations:

Kfa(x)＝KFA*sin(2*pi*x/(2*mp))

Kfb(x)＝KFB*sin(2*pi*x/(2*mp)-2*pi/3)

KFC (x) ═ KFC sin (2 × pi x/(2 × mp) -4 × pi/3), wherein

x: relative position of the plunger 12 in the axial direction 14 with respect to the coil pairs 28a/28b, 30a/30b, and 32a/32b

mp: magnetic or polar distance 40

KF(_A-C): constants dependent on actuator design

The method for determining the phase force constant in real conditions is well understood and therefore not described in detail. It should be understood, however, that while an ideal example for the phase force constant is described herein, this is for exemplary purposes only and the phase force constant may be defined by known methods in actuator design.

As reflected by the above equation, when phase _ shift is 0 (i.e., when ia (x), ib (x), and ic (x) correspond exactly to the q-axis current), ia (x) is in phase with Kfa (x), ib (x) is in phase with Kfb (x), and ic (x) is in phase with Kfc (x). Force F between plunger and stator_outIs the sum of the products of each current signal multiplied by its corresponding phase force constant. FIG. 6 shows F contributed by ia (x) and Kfa (x)_outA part of (a). It should be understood that ia (ia)x) completely includes the q-axis current, so the force curve has a dc offset that makes the entire force curve positive and frequency doubled. F contributed by ib (x) and Kfb (x) and ic (x) and Kfc (x)_outThe other two components have the same shape of the curve as shown in fig. 6, but they are offset by 120 ° from each other and by 120 ° relative to the components contributed by ia (x) and kfa (x). F as a sum of three components_outIs a constant force, and thus the three-phase actuator 10 applies a constant force to the plunger 12 by applying the three-phase currents ia (x), ib (x), and ic (x) to the respective coil pairs.

Adding a non-zero phase _ shift to current ia (x) shifts the phase of the ia (x) curve relative to its phase force constant curve, thereby reducing the dc offset of the force curve shown in fig. 6, such that a portion of the force curve is negative. When the same phase _ shift is applied to each of the other two current signals ib (x) and ic (x), the same reduction in dc offset occurs in their respective force curves. F for which the sum of the three force curves is still constant_outBut constant F_outIs lower than the value when phase _ shift is 0. When phase _ shift is 90 °, i.e., when the air gap flux density curve generated by the coil current signal is 180 ° out of phase with its corresponding air gap flux density curve from the plunger permanent magnet, F_outIs 0. Similar to the electrical q-axis phase, however, the particular phase _ shift in the least efficient application where coil current is present will likely be slightly different from the ideal 90 ° shift. The current at this electrical phase shift relative to the q-axis current is referred to as the "d-axis" current. It is known to apply a d-axis current component to drive a motor operating in a field-weakening, steady-state type environment, thereby extending the upper speed range of the motor without the need to use a higher voltage supply. Although a plunger having a plurality of permanent magnets is described in this example, it will be understood by those skilled in the art in light of this disclosure that the systems and methods described herein may be implemented using a rod having a plurality of magnets, some or all of which may be permanent magnets or electromagnets.

It should be understood that the coil currents may be described by individual coil currents ia (x), ib (x), and ic (x), or by q-axis components iq (x) and d-axis components id (x). The synchronous coordinate transformation between these descriptions should be well understood:

iqs (x) ia (x), and

ids (x) ib (x) 1/(3)1/2-ic (x) 1/(3)1/2 and

I_q(x) Iqs (x) cos (phase) -sin (phase)), and

I_d(x) Ids (x) ((sin) (phase) + (phase)), wherein

Phase: the phase _ shift is set to a value of,

iqs (x): the q-axis current in the stationary reference frame,

ids (x): the d-axis current in the stationary reference frame,

I_q(x) The method comprises the following steps Q-axis current in a rotating reference frame, an

I_d(x) The method comprises the following steps Rotating the d-axis current in the reference frame.

In the case where coil current signals ia (x), ib (x), and ic (x) all include d-axis current, the stator coils apply no net force to the plunger, or a minimum force to the plunger within the possible range of forces that the system may apply. If the controlled current on the coil comprises a mixture of q-axis and d-axis currents, and if the maximum transient current values Ia, Ib and Ic are the same in the three cases, the actuator applies a force to the plunger with an amplitude between the minimum force generated with a full d-axis current and the maximum force generated with a full q-axis current. Note that because the maximum current remains the same in all three cases (i.e., full q-axis current, full d-axis current, and mixed q-axis and d-axis current), the actuator consumes the same amount of power in all three cases.

For one exemplary arrangement and as will be described in greater detail below, it is now assumed that the actuator 10 is part of a vehicle suspension system such that the plunger 12 is directly connected to the wheel assembly 15 or suspension system for the seat, and the stator 16 is sufficiently close to the seat such that heat is transferred from the stator 16 to the seat. Under normal circumstances, the motor control systems 17 (fig. 1) and 21 sense the position and/or velocity of the plunger 12 and determine the corrective force applied to the plunger by corresponding instructions 19 to the inverter 34, the instructions 19 resulting in a response of the wheel suspension or seat that improves handling of the vehicle and/or comfort for the vehicle operator seated in the seat, or heats the seat suspension module or actuator to raise its temperature to a suitable operating temperature, for example when the ambient temperature is below the normal operating temperature of the suspension module (such as 0 ℃). The force correction may be determined by the processor 58, but in another embodiment is determined by a separate processor that provides force commands to the processor 58. A system for determining and applying such desired force to a seat in a vehicle is described in, for example, co-pending U.S. patent application 10/978,105 entitled "activesuspension" filed on 29/10/2004, which is hereby incorporated by reference in its entirety. The specific corrective algorithm itself is not part of this embodiment and a detailed discussion of the algorithm itself is omitted here. However, at any given moment during activation of the control system 17 or 21, the control system defines such force command, and the inverter 34 defines the maximum transient current amplitudes Ia, Ib and Ic for the respective three-phase coil pair based on the force command (either determined directly or by determining the q-axis and d-axis components for the control system 21), which will result in a predetermined, desired, zero or non-zero force to be applied to the plunger. As mentioned above, it is known to determine the maximum current amplitude of such a full q-axis current. However, in one presently described embodiment, and referring to FIG. 3, if the vehicle operator activates a switch to initiate the seat warming function, or when a sensor such as a temperature sensor detects that the ambient temperature of the actuator is below its operating temperature, a seat heating signal is sent to the control system 21. The control system 21 performs the functions of the control system 17 (fig. 1) discussed above, but in addition to this, the control system 21 introduces phase _ shift to the three-phase current (which is also described as adding the d-axis component) in response to the seat heating request signal. Since phase _ shift has the effect of reducing the force applied to the plunger if maximum current amplitudes Ia, Ib, and Ic remain the same as when phase _ shift is 0, the maximum current amplitudes (Ia, Ib, and Ic) can be increased by an amount sufficient to maintain the desired force defined by the corrective algorithm. In one specific example, discussed below, this effect is achieved by: the q-axis current required to achieve the desired force is determined, and the d-axis component is added to generate additional desired heat. That is, maintaining the q-axis component while adding the d-axis component results in phase _ shift being added while increasing the maximum current amplitude to maintain the desired force on the plunger.

Alternatively, where the system determines phase _ shift by phase rather than by d-axis component, the desired F_outThe phase force constants, relative stator/plunger positions and pole pitch are known, and the defined phase _ shift yields the desired F_outThe required currents Ia, Ib and Ic can be determined by the above equations. Thus, according to either method, a d-axis component is applied, and the force applied to the plunger in the presence of a phase _ shift/d-axis component is equal to the desired force defined by the corrective algorithm and is the same force that the actuator would apply to the plunger in the absence of a phase _ shift/d-axis component. However, due to the phase _ shift/d axis component, the control system controls for greater current dissipated on the stator coils when this same force is achieved. That is, to achieve the same force, more power is consumed, resulting in more heat being generated.

The effect of this added d-axis current in this exemplary arrangement can be described with reference to the force diagram shown in fig. 2. The system may periodically determine (at a sampling frequency) a desired force to be applied to the plunger 12 (fig. 3) in accordance with a force correction algorithm. As mentioned above, this force is derived from the q-axis current or I_q. However, since the user has requested seat heating, the system also desires to apply a predetermined current level to the actuator coil to provide heat represented by dissipated power 6. Such an apparatus for consumingThe current that dissipates heat without being used for the force applied to the plunger is the d-axis current I_d. It will be appreciated that the q-axis current also contributes to the heat dissipated in the coil, and that an increase in the q-axis current (if desired) may therefore serve to further increase the heat generated, but this will also increase the force applied to the plunger. Thus, the use of d-axis current addition allows heat to be generated without altering the desired force applied to the plunger.

The request for seat heating in this embodiment corresponds to a request for a predetermined dissipated power 6. It should be appreciated that the system may provide the user with a choice between a plurality of seat heating levels, each corresponding to a respective desired dissipated power level 6, through a plurality of toggle selection options. The coil resistance is known and the processor 58 estimates the actual dissipated power 6 at any given moment, as described below. If the actual dissipated power is lower than the desired dissipated power, the total current level IT should be increased to bring the dissipated power up to the desired level. The total current level IT is the geometric sum of the q-axis current and the d-axis current, or

I_T＝(I_q ²+I_d ²)^1/2，

Wherein I_qAnd I_dIn a rotating reference frame. Referring to coil 26a (fig. 3), Ia at a given instant (i.e. a given position x of the plunger 12 (fig. 3) relative to the stator) may be considered to be I for that coil at that instant_T. The transient currents Ib and Ic of the other two coils can be considered similarly. As described above, processor 58 receives the q-axis current I required to determine a given time instant_qThe force command of (1). Accordingly, based on the above description about I_TAnd known coil resistance, processor 58 determines whether Ia (i.e., I of coil 26 a) is to be measured_T) To I sufficient to produce the desired dissipated power level_dThe value of (c). I is_qAnd I_dThe relationship between them defines phase _ shift. The control system 21 controls the suspension actuator 10 to obtain the determined total current at this phase _ shift, i.e. to obtain a current comprising for each of the three coils of the actuator a current value for each of the three coils of the actuatorThe total current of these q-axis and d-axis components. Since the power can be described as I²R, where I is the current and R is the coil resistance, so the transient dissipated power 6 is (I)_q ²+I_d ²) R plus core losses and amplifier losses.

Thus, the transient dissipated power 6 and amplifier losses from the q-axis current and the d-axis current may be considered known or determinable (albeit dynamic) values, as may the q-axis current-derived force F between the suspension actuator 10 and the plunger 12_outThat way. F_outContributes to the speed of the plunger 12 and thus to the actuator mechanical power 2, but the magnitude and direction of the mechanical power 2 is also significantly affected by other external forces applied to the plunger 12. Thus, based on F_outAnd these external forces applied to the actuator 10, the plunger 12 has a velocity relative to the stator 16 (fig. 3), and this velocity defines the actuator mechanical power 2 (specifically, velocity multiplied by F) having a magnitude and direction_out) I.e. either into the actuator 10 or out of the actuator 10 as shown in fig. 2. Since the three interface power must sum to zero (i.e., the total power flowing into the actuator 10 must equal the total power flowing out of the actuator 10), the dissipated power and the real actuator mechanical power 2 described above define the direction and magnitude of the DC bus power 4. If F_outAnd the speed of the plunger 12 are in the same direction, mechanical power 2 flows out of the actuator 10 (i.e. to the right in fig. 2), and thus DC bus power 4 must flow into the actuator 10 and have an amplitude equal to the sum of the amplitudes of mechanical power 2 and dissipated power 6. Therefore, the battery 11 must provide I_qAnd I_dAll currents required. On the other hand, if F_outAnd the direction of the plunger velocity (i.e., if the force correction algorithm causes the control system and suspension actuator to apply a force to the plunger that is opposite the actual direction of motion of the plunger at that instant), then actuator mechanical power 2 flows into the actuator 10 (i.e., to the left in fig. 2). If the amplitude of the mechanical power 2 is smaller than the amplitude of the dissipated power 6, the DC bus power 4 has to flow into the actuator 10 and have an amplitude equal to the difference in amplitude between the mechanical power 2 and the dissipated power 6. As described in more detail belowIn this case, the battery 11 and the mechanical power are both current sources for the actuator 10 to provide the required q-axis current and d-axis current, as described in detail. If the magnitude of the mechanical power 2 is greater than the magnitude of the dissipated power 6, then DC bus power 4 flows out of the actuator 10 onto the DC bus, causing a regeneration event to occur. The amplitude of the DC bus power 4 is the difference in amplitude between the mechanical power 2 and the dissipated power 6. In this case, the mechanical power provides a current source for the q-axis current and the d-axis current and returns the current onto the DC bus and into the battery 11, so that the actuator 10 acts as a generator.

The regenerative current flowing into the battery 11 can recharge the battery and is somewhat beneficial. However, regeneration events may have the following severity: directing the current level onto the DC bus will damage the battery or reduce its useful life. This situation may result, for example, in the case where the actuator 10 is part of a vehicle suspension system, in having the plunger 10 directly connected to the wheel assembly 15 (in a four wheel drive vehicle there are four actuators, one for each wheel). The stator housing may be connected to the vehicle chassis 25 and the plunger may be connected to the wheel assembly. When a vehicle passes through a deceleration barrier or severe bore (severe hole) in a roadway, the ram is typically at F_outSuddenly moving in the opposite direction at a significant speed. Thus, it is known to place substantially parallel capacitors (e.g., capacitor 23, as shown in fig. 1) on the DC bus so that regenerated energy (sometimes referred to as regenerated pulses) can be stored and the stored current discharged back onto the DC bus. A properly designed capacitor may operate effectively and reliably in this manner, but the incremental component cost and additional physical volume requirements needed to provide sufficient capacitance to accommodate significant regeneration events may be undesirable, particularly in vehicular applications.

Thus, as described in more detail below, the control system 21 may monitor the position and speed of the plunger 12 and, after detecting a regeneration event that exceeds or is likely to exceed a predetermined maximum power level (or energy level over a period of time), increase the d-axis current component discussed above, preferably so that the DC bus power 4 is reduced so that the resulting current will not damage the battery system. Regenerative compensation can be implemented with or without the application of d-axis current to the seat heating, the simultaneous application of both processes simply adding more d-axis current to the coil than just one process.

It should be understood in the art that any electric actuator system will define the maximum output torque or force that can be achieved, typically due primarily to thermal limitations on the motor or amplifier. Due to heat and total current I of the amplifier_TAre proportional, so it is understood that the pair I can be defined_TThe limit of (2). If for a given motor, adding the d-axis component to the current results in a total current I that exceeds this threshold_TThen the d-axis current delta is decreased until the total current is below the threshold.

The presently described embodiments are discussed in the context of a current controlled, commutated actuator. It should be appreciated that although the present discussion is primarily directed to brushless DC actuators, the present invention may be implemented as part of an induction motor control system. It will be appreciated that in such a configuration, slip needs to be considered when expressing the output force (torque for a rotating AC machine) in terms of a q-axis component aligned with the rotor flux. Thus, for example, the invention may be implemented as a current controlled rectified induction AC induction machine. "commutation" refers to the control of current in an actuator based on the relationship between the position of a rod (e.g., rotor or plunger) and an amplifier.

An inverter is an amplifier that provides an alternating voltage signal to the coil. The adjustment to the inverter duty cycle is an adjustment to the variable gain of the amplifier, and a given gain results in an alternating average current signal across the coil pair. This alternating average current is the alternating current signal that produces the alternating air gap flux density shown in fig. 5. Thus, the control circuit defines the amplitude of the current signals applied to the motor coils, the phase of the current signals relative to each other, and the phase of the curve of the air-gap flux density caused by the current relative to the curve defined by the air-gap flux density formed by the plunger magnets. Although a voltage source inverter is described, other inverters, such as current source inverters, may be applied.

When the plunger moves rapidly in response to a regeneration event, the resulting back emf of each coil pair 28, 30 and 32 may be large. In the case where the inverter applies a current signal to the actuator coil to apply a force to the plunger in a direction opposite to the plunger velocity, the electromotive force opposes the voltage signal applied to the coil by the inverter, and in cases such as potholes or deceleration barriers, a significant current (regenerative current) may flow back onto the DC bus through the diode of the inverter. That is, a significant increase in the lead voltage of the coil significantly reduces the system displacement power factor (the time phase relationship between the inverter output voltage and the current), thereby significantly increasing the power returned to the source, and thus the current regenerated to the DC bus.

In the presently described embodiment, the displacement power factor is effectively increased due to the additional real power dissipated in the motor coils due to the d-axis current component, thereby reducing the net current applied back to the power supply 42 through the DC bus. That is, the power factor is increased by: the power applied by the system power supply is increased so that it is at or near the load power, thereby reducing or substantially eliminating power reflected back to the system power supply.

The effect on the control of the d-axis current component on the actuator coil is illustrated by the phase diagrams shown in fig. 7 to 9. Each phase diagram shows the current and voltage drop in a circuit comprising a battery/inverter (seen as a single voltage source), the resistance of one of the coil pairs, the inductance of one of the coil pairs, and if applicable also the back emf. ' V_amp"refers to the voltage across the battery/inverter source. ' V_R"refers to the voltage across the coil resistance. ' V_L"refers to the voltage across the coil inductance. "R" refers to the coil resistance. "L" refers to the coil inductance. IP refers to the total current in the circuit. "I_D"means I_PThe d-axis component of (a). "I_Q"means I_PQ-axis component of (a).

Referring to fig. 7, if it is desired to apply a force to the rod by applying a current to the stator coils, as described above, an effective way to achieve this is:

(1) knowing the speed of relative movement between the stator and the rod,

(2) knowing the pole pitch of the bar magnet,

(3) from these two pieces of information, the frequency of the magnetic flux signal across the air gap from the stator is determined,

(4) knowing the relationship between the current in the coil and the resulting force on the rod when the current is a q-axis current,

(5) knowing the magnitude of the force desired to be applied to the rod, an

(6) Controlling the inverters to define the voltage signal V at the frequency (timed such that the voltage signal varies in phase with the electrical q-axis) and in amplitude defined in (3)_ampTo generate a current IP which (through the relationship defined in (4)) results in the force defined in (5).

However, it is understood in the art that the rod generates a back electromotive force (V) according to the following relationship_emf)：

V_emf＝dFlux/dt＝(dFlux/dx)*(dx/dt)

Where "Flux" is the air gap Flux density profile contributed by the plunger magnet (FIG. 4) and dx/dt is the plunger velocity. Therefore, if the rod moves in the direction in which the q-axis current applies force to the rod, the counter electromotive force is always in phase with the q-axis current, and if the rod moves in the direction opposite to the direction in which the q-axis current applies force to the rod, the counter electromotive force is always 180 ° out of phase with the q-axis current.

In FIG. 7, control V_ampTo apply only q-axis current and the rod moves in the direction of the force applied by the q-axis current to the rod, so that V_emfIn phase with the q-axis current. This means that V_emfAnd V_RIn phase, the voltage drops across the resistor.

It is understood in the art that V_ampAnd I_pThe angle between theta relates to a power factor that depends on the cosine of theta. If COS θ is positive, the power factor is positive and there is no regeneration current in the system. If COS θ is negative, the power factor is negative and there is a regenerative current in the system. The formula for solving for Ip is:

as shown in fig. 7, COS θ is positive. Thus, the power factor is positive and there is no regenerative current.

In fig. 8, the rod moves in a direction opposite to the direction in which the q-axis coil current applies to the rod. Likewise, V_ampIs fixed by an inverter. V_emfIs negative. I is_pAlso given by the following equation:

since in this example V_emfIs greater than V_ampSo as shown in FIG. 8, I_PMust be positive. θ is between 90 ° and 270 °; the power factor is negative and a regenerative current occurs.

Referring also to FIG. 9, if the inverter is controlled to direct the d-axis component into V during such a regeneration event_ampThen, I_PAlso includes a d-axis component, and I_P＝(I_Q ²+I_D ²)^1/2. Due to V_emfAlways with q-axis current I_QIn phase or with a phase difference of 180 DEG, so that V_emfAnd I_QCalibration, not I_PAnd I is_QRelative to V_emfAnd is angled. Such as aboveIn the example and necessarily as described in the example above, V is shown in FIG. 9_ampIs V_emf、V_RAnd V_LThe vector sum of (1). Thus, if V is given_ampAmplitude of (V)_emfAmplitude of (1) and_Pthe phase shift in (i.e., the addition of the d-axis component) then I can be determined_POf the amplitude of (c). This in turn determines V_ampRelative to V_emfAnd θ. As shown in FIG. 9, in this arrangement, the direction I_PAdding a phase shift lowers θ. If towards I_PAdding enough phase shift to drop θ below 90 °, the power factor becomes positive and there is no regenerative current on the DC bus.

When the system is operating in the linear range, in other words, when there is no magnetic saturation, adding the d-axis current component to the current applied by the inverter to the actuator does not affect the q-axis component. It remains the same. Thus, the addition of the d-axis component increases the total current applied to the actuator, but does not affect the current defined by the suspension algorithm for applying force to the plunger. Thus, the step of determining the d-axis current component and applying the d-axis current component to the inverter output does not affect the application of the current signal in response to the suspension algorithm.

Referring to fig. 3-10, a control system for the suspension actuator 10 may include circuitry including a processor 58 and a synchronous frame current regulator 60 that controls the inverter 34. The exemplary control system has 4 inputs: linear position X of the motor_PCurrent (i) of coil 26a_a) Current (i) of coil 26b_b) And force command F from a suspension controller (not shown)_P. Linear position X of the motor_PRefers to the position of the plunger 12 relative to the stator 16 as measured by the linear encoder 62, which linear encoder 62 may be considered part of the control system. Linear encoders are well understood high precision sensors capable of measuring mechanical displacement of the plunger 12 relative to the stator 16 to an accuracy of up to 0.01 millimeters (mm), but it should be understood that different types of sensors may be used, or other accuracies may be used, so long as the sensors are tailored to the system accuracy requirements. In a machine comprising a rotary actuatorIn an embodiment, for example, a rotary encoder may be used. Generally, where sensors are used, the sensors may be selected to match the physical relationship between the stator and the rod.

The linear encoder 62 outputs a signal to the current regulator 60 that describes the relative mechanical displacement between the plunger and the stator. In the presently described embodiment, the processor 58 is a digital controller that operates at a sampling rate of 8kHz in this example.

Fig. 10 shows process steps in an exemplary regeneration compensation of functional blocks executed by a processor running in software. With the processor 58 receiving the sampled position data from the linear encoder 62 through the current regulator 60, the position data (in mm) X_P(i.e., the relative position between the stator and the rod as described above) is provided to a mechanical position to electrical phase block 64, and the mechanical position to electrical phase block 64 converts the linear distance data into a phase for output at 66. As described above, the pole pitch of the plunger is known. Since the polar distance corresponds to 1pi (1 pi) radians, the mechanical position to electrical phase block 64 passes the sampled (relative) position data X_PMultiplied by pi/(pole pitch) to determine the phase output 66. Since the phase output 66 describes the phase position between the plunger 12 and the stator 16, and specifically the relative phase between the stator coil and the plunger poles, the phase output 66 describes the actual relative phase between the air-gap flux density profile contributed by the plunger magnet (fig. 4) and the air-gap flux density profile contributed by the coil (fig. 5).

It should be understood in the art that the linear encoder 62 also provides sufficient information to determine the plunger velocity by sampling the position data over time, although it should also be understood that some linear encoders may provide velocity as a direct output signal.

The system includes a current sensor on the amplifier DC bus that directly measures the DC bus current. In one example, two of the three phase currents are measured. As shown at 74, the current regulator 60 samples the amplitudes ia and ib (in amperes) of the actual currents on the coils 26a and 26b (at a rate of 8 kHz). The current regulator, including its pair of plunger/rotor position and motor current magnitude and phase, should be well understood and thus not discussed further herein. In the presently described system, the current regulator 60 comprises a software component of the processor 58 (and thus may be considered part of the blocks for the processor 58 of fig. 3), but a current regulator comprising a hardware component may also be used.

The instantaneous magnitude of the current on coils 26a and 26b also defines the instantaneous magnitude of the current on coil 26c, since the currents on the three coils must add to 0 according to kirchhoff's current law. The Q-axis DC bus power estimator block 68 determines the actual Q-axis and d-axis currents on the DC bus based on the actual current amplitudes on the three coils at the sampling instant, the mechanical phase between the plunger and stator at that instant as described above, and predetermined calibration information for the particular motor regarding the actual Q-axis offset. Methods for estimating the q-axis current and the d-axis current from such information are understood in the art and thus will not be described in detail herein.

Having determined the Q-axis current and the d-axis current on the actuator coil wire, a Q-axis DC bus power estimator 68 estimates the dissipated power 6 (fig. 2) in the coil that originates from the Q-axis current. For q-axis current, the power from the coil loss is (I)_q ²)*(3/2)*R_PWherein R is_PIs the coil resistance per phase. However, the dissipated power (i.e. I) due to the resistance of the coil²R losses) does not constitute all the dissipated power. The coil resistive losses may amount to about 70% of the total dissipated power 6, although it should be understood that the actual percentage for a given actuator may vary with the design and manufacture of the actuator, with the remainder including power electronics losses, core losses, and possibly other sources of loss. The contribution to dissipated power 6 caused by power electronics losses (mainly losses in inverter/amplifier 34) and motor core losses should be known from the design of a given actuator, and estimator block 68 adds this estimate to the coil resistance losses (for each coil pair) so that the final summation is for linear encoder 62 to be electricalThe flow is subjected to an estimation of the dissipated power 6 at the sampling instant. The contribution to dissipated power caused by power electronics losses, motor core losses, and other losses can be predicted from the q-axis current. Thus, in one example, controller 21 stores a look-up table for defining such losses by q-axis current, such that processor 58/block 68 looks up these other losses from the table given the q-axis current determined in estimator block 68.

The estimator block 68 then estimates the actual actuator mechanical power 2 (fig. 2). The actual mechanical power between the stator and the plunger is F_outMultiplied by the actual speed of the plunger. As described above, the control system derives the velocity of the plunger from the position data obtained by the linear encoder 62. Thus, the estimator block 68 determines F based on the actual q-axis current determined as described above_out. Since the d-axis current does not contribute to the force applied to the plunger, the d-axis current is not used to determine F_out. According to the q-axis current:

F_outiq × Kf, wherein:

iq is the overall transient q-axis current over the three coils as determined by estimator block 68; and

Kf＝1.5*Max(Kfa(x)，Kfb(x)，Kfc(x))

estimator 68 now has F at the sampling instant_outAnd plunger speed, these values being multiplied to determine the mechanical power 2. The sign of the mechanical power 2 (i.e. whether the mechanical power flows into or out of the actuator 10) is determined by the direction of the plunger speed. If the speed is equal to F_outIs the same, the mechanical power is positive (i.e. out of the actuator). Otherwise, the mechanical power 2 is negative (i.e. flows into the actuator). As mentioned above, the dissipated power 6 flows out of the actuator and may be considered positive for this discussion. The estimator 68 sums the dissipated power 6 and the actual mechanical power 2. Results P_{q axis}Is the power on the DC bus that would be present if the actuator were controlled to apply only q-axis current to the coil. If the result is positive, the DC bus power 4 is positive, i.e. in this case the DC bus power 4 will flowAnd an actuator. This situation occurs if both dissipated power 6 and mechanical power 2 flow out of the actuator, or if mechanical power 2 flows into the actuator but dissipated power 6 is greater than mechanical power 2. If the result is negative, i.e. if the mechanical power 2 flows into the actuator and is greater than the dissipated power 6, a regeneration event will occur.

At 70, the estimator 68 outputs the estimated DC bus power P to the power-to-current converter function 72_{q axis}(including its sign, i.e., positive if flowing into the actuator and negative if flowing out of the actuator). The transducer 72 also receives plunger position data X from the mechanical position block 64, as shown at 74_PAnd receives the actual current amplitude on coils 26a and 26b from current regulator 60.

Fig. 11 expands the converter 72 into an example of its component functional blocks. Thus, referring to fig. 3, 10 and 11, at block 76 the converter 72 will estimate the DC bus power P_{q axis}Compared to a predetermined DC bus power limit. The predetermined limit corresponds to a regenerated (i.e. negative) power level on the DC bus, and the predetermined limit is preferably set to a negative power level that allows regeneration to the extent: regeneration is either absorbed by the bus capacitance or the battery is beneficially recharged without undesirably damaging the battery. It should be understood that the configuration of batteries made by different manufacturers or the configuration of different types of batteries made by a given manufacturer may vary. If the desired battery life and power characteristics are known, the battery manufacturer may generally provide a peak regenerative current that is accepted by the battery to achieve these properties, and such peak level may be used to determine the power level for use as the predetermined level used at decision block 76. Thus, the predetermined limit may vary in systems using different batteries.

If P is_{q axis}Exceeding a predetermined regeneration level P_Limiting(or P in case both values are considered negative_{q axis}Below a predetermined regeneration level P_Limiting) Then the summing block 78 determines P_{q axis}And P_LimitingThe difference between them.Results P_{d axis}Is the d-axis power, which is expected to be dissipated as part of the dissipated power 6. At 80, P is applied to the smoothing filter_{d axis}To smooth the step functions provided by 76 and 78 before application to the current regulator.

At 82, the converter 72 converts the desired d-axis power to a desired d-axis current. The block 82 receives the desired d-axis power P from the smoothing filter 80_{d axis}And receives the measured actual coil q-axis current from the synchronous frame transform block 84. The transformation block 84 receives phase currents from the coils 26a and 26b, the phase currents of the coils 26a and 26b defining the transient current magnitude on the coil 26c and the phase of the plunger relative to the stator as described above. Block 84 determines a total actual coil current I from the three coil currents_q. Block 84 then uses the plunger phase to determine the q-axis component I of this current as described above_q. Application of the formula P shown in Block 82 of FIG. 11_{d axis}、I_qAnd R (where R is a per-phase resistance), converter 72 determines the d-axis current I that will produce the desired additional power loss in the motor coils and thereby limit the regenerative power on the DC bus_d’。

At block 85, converter 72 measures the actual q-axis current I_qAnd a desired d-axis current I_d' combine the total current value and compare this value to the total current limit. As mentioned above, the system current preferably does not exceed a predetermined maximum level. If the combined actual q-axis current and desired d-axis current exceed predetermined limits, converter 72 will convert I_d' reduction to value I_d ^*Until the combined total current falls within acceptable levels.

The function block 86 provides saturation compensation for the q-axis current level. It will be appreciated that as the current in the coil increases, the magnetic flux generated by the coil current does not increase linearly due to saturation effects. Block 86 determines an adjustment to the q-axis current to account for saturation effects, with an output of I_{q_delta}. The saturation effect can be described as a decreasing force constant with increasing coil current, anAnd is a function of the specific motor/actuator design, which may be determined by model or by testing based on the manufacturer's motor information. Thus, saturation effects may be stored in a look-up table such that for a given I_d ^*And I_qConverter 72 simply selects I from the look-up table_{q_delta}. The output of block 86, and thus the output of converter block 72, is the desired d-axis current I_d ^*And the desired change in q-axis current I_{q_delta}。

If the regenerative power measured at 76 is less than P_LimitingThen, I_d ^*And I_{q_delta}Is set to 0.

The control system receives force commands from the suspension controller via motor force constant profile block 88And defines the desired q-axis current based on that input. The force command is the requested force that the suspension controller calculates should be applied to the plunger to achieve the desired effect. Block 88 converts this force command into the q-axis motor current value required to generate that force in the actuator. Thus, for any given force command input, block 88 determines the desired q-axis current I from the lookup table_qp. Desired q-axis current I_qpIs summed at summation block 90_{q_delta}And (5) modifying. The control system outputs the obtained q-axis current command I to the current regulator 60_q ^*And d-axis current command I_d ^*。

In another exemplary arrangement, the system includes a plurality of actuators and a control system. For example, a vehicle may have four or more wheels in the suspension system, each wheel having its own actuator 10 (fig. 3) controlled by a respective amplifier 34. Four (or more or less, depending on the number of wheels) amplifiers are deployed in parallel with respect to each other, capacitor 23 and battery 11. Each amplifier is controlled by the same processor 58 to control the mixing of the d and q currents, but each amplifier implements a separate current regulator 60. Each having its own linear amplifier 62.

In this arrangement, transient regenerative current from any one of the amplifiers may be dissipated in one or more of the other amplifiers. Thus, to the extent that the other amplifiers are not experiencing a regeneration event, the current from the regenerative amplifier flows to the non-regenerative amplifier rather than to the battery. Referring also to fig. 10 and 11, processor 58 determines P for each amplifier simultaneously_{q axis}. For each individual amplifier, at block 76, the processor 58 receives P from the plurality of actuators of each respective estimator block 68_{q axis}And sums them. As described above, P if power flows into the corresponding actuator_{q axis}Is positive and negative if flowing out (i.e., if a regeneration event occurs for that actuator), so a plurality of P s_{q axis}The sum of the terms is the power seen by the battery across all actuators. This sum is summed with P as described above_LimitingThe comparison determines whether the d-axis component should be added to the current of the regenerative actuator.

While one or more embodiments of the invention have been described above, it should be understood that the scope and spirit of the invention includes any and all equivalent implementations of the invention. Accordingly, the embodiments presented herein are merely examples and are not intended to limit the present invention. Accordingly, any and all embodiments that may fall within the scope of the following claims are intended to be encompassed by the present invention.

Claims (24)

1. A method of controlling an actuator having a stator, a rod, at least one coil, and a power source, wherein the rod has a plurality of magnets, the stator and the rod move relative to each other at an interface between the stator and the rod such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface, the at least one coil is disposed on the stator relative to the interface such that a current applied to the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to changes in the current, the power source has a voltage, the method comprising the steps of:

(a) applying the voltage across the at least one coil at a variable level;

(b) determining a relative position between the stator and the rod;

(c) receiving a first input comprising a signal indicative of a request for a force to be applied to the rod;

(d) receiving a second input comprising a signal indicative of a request to dissipate heat in the at least one coil;

(e) controlling the variable level to provide a q-axis component of current on the at least one coil in response to the relative position and the first input to vary the second magnetic flux; and

(f) controlling the variable level to provide a d-axis component of current on the at least one coil in response to the second input to vary the second magnetic flux to dissipate heat in the at least one coil while maintaining the force to be applied to the bar.

2. The method of claim 1, wherein the second input carries information indicating the presence of a regeneration event.

3. The method of claim 2, wherein the regeneration event indicates that current is present between the power source and the at least one coil, the method comprising the steps of:

wherein the step (d) comprises the steps of:

(g) determining the power dissipated in the at least one coil,

(h) the mechanical power on the rod is determined,

(i) determining power on a bus between the power source and the at least one coil based on the dissipated power determined in step (g) and the mechanical power determined in step (h),

(j) (ii) comparing the bus power determined in step (i) with a predetermined criterion indicative of the presence of regenerative current to the power supply to produce an indication signal, and

wherein step (f) comprises shifting the phase of the current on the at least one coil to introduce the d-axis component when the signal in step (j) is indicative of a regenerative current.

4. The method of claim 1, including the step of storing a predetermined phase shift corresponding to a predetermined said d-axis component, and wherein step (f) includes shifting the phase of the current on said at least one coil by the predetermined phase shift to introduce the predetermined d-axis component in response to receipt of said signal indicative of a request to dissipate heat in said at least one coil.

5. An apparatus and a control system in a vehicle, wherein the control system is for actively suspending the apparatus in the vehicle, comprising:

the device changing position relative to the vehicle in response to a force determined by the control system;

an electrically commutated actuator, comprising:

a stator which is provided with a plurality of stator coils,

a rod having a plurality of magnets, the stator and the rod moving relative to each other at an interface between the stator and the rod,

wherein the plurality of magnets are disposed relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface, an

At least one coil disposed on the stator relative to the interface such that a current on the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to variations in the current, and

wherein the rod is in mechanical communication with the device such that a force is applied to the device through the rod;

a power supply having a voltage;

a variable amplifier electrically disposed between the power source and the at least one coil such that the amplifier applies the voltage across the at least one coil at a variable level;

a sensor disposed relative to at least one of the stator and the rod such that the sensor detects a relative position between the stator and the rod, wherein the sensor outputs a signal corresponding to the relative position; and

the control circuit:

receiving a first input and a second input, wherein the first input comprises a signal indicative of a request for a force to be applied to the bar and the second input comprises a signal indicative of a request to dissipate heat in the at least one coil,

receiving a signal from the sensor or sensors and,

controlling the variable amplifier such that the variable level varies in response to the relative position and the first input to provide a q-axis component of current on the at least one coil, an

Controlling the variable amplifier such that the variable level varies in response to the second input, thereby providing a d-axis component of current on the at least one coil to dissipate heat in the at least one coil while maintaining the force to be applied to the bar.

6. The apparatus and control system of claim 5, wherein said control system outputs a command comprising said first input.

7. The device and control system according to claim 5, comprising a user-activatable switch that outputs a signal comprising the second input.

8. The appliance and control system of claim 5 including a sensor that detects ambient temperature and outputs a signal including the second input when the detected ambient temperature is below a predetermined value.

9. The apparatus and control system of claim 5, wherein the control circuit stores a predetermined phase shift corresponding to a predetermined d-axis component, and wherein the control circuit shifts the phase of the current on the at least one coil by the predetermined phase shift to introduce the predetermined d-axis component in response to receipt of the signal indicative of the request to dissipate heat in the at least one coil.

10. The apparatus and control system according to claim 5, comprising three of said at least one coil disposed in a three-phase configuration relative to said shaft and said amplifier.

11. The apparatus and control system of claim 5 wherein said control circuit defines a maximum total current in said at least one coil, and wherein when an aggregate of said q-axis component and said d-axis component exceeds said maximum total current, said control circuit decreases said d-axis component so that said aggregate does not exceed said maximum total current.

12. The appliance and control system of claim 5, wherein the second input carries information indicating the presence of a regeneration event.

13. The apparatus and control system according to claim 5, wherein:

the control circuit includes a processor configured to:

determining the power dissipated in the at least one coil,

the mechanical power on the rod is determined,

determining a power on a bus between the battery and the at least one coil based on the dissipated power and the mechanical power to produce an indication signal, an

Wherein the control circuit is configured to shift a phase of a current on the at least one coil to introduce the d-axis component when the indication signal corresponding to the comparison indicates a regenerative current.

14. An electrically commutated actuator and control system, comprising:

a stator;

a rod movable relative to the stator at an interface between the rod and the stator;

a plurality of magnets movable relative to the rod, wherein the plurality of magnets are disposed relative to the interface such that the plurality of magnets provide a first magnetic flux that varies in magnitude and direction along the interface;

at least one coil disposed on the stator relative to the interface such that a current on the at least one coil provides a second magnetic flux that varies in magnitude and direction along the interface in response to changes in the current;

a variable amplifier applying a varying current across the at least one coil, the varying current including a q-axis component and a d-axis component; and

a control circuit that defines the q-axis component in response to a first input and variably defines the d-axis component relative to the q-axis component in response to a second input to dissipate heat in the at least one coil while maintaining the force to be applied to the bar, wherein the first input includes a signal indicative of a request for force to be applied to the bar and the second input includes a signal indicative of a request for heat to be dissipated in the at least one coil.

15. The electrically commutated actuator and control system of claim 14, constructed and arranged to actively suspend a device in a vehicle.

16. The electrically commutated actuator and control system of claim 14, wherein said control system output comprises a command of said first input.

17. The electrically commutated actuator and control system of claim 14, comprising a user-activatable switch that outputs a signal comprising said second input.

18. The electrically commutated actuator and control system of claim 14, comprising a sensor that senses an ambient temperature and outputs a signal comprising said second input when the sensed ambient temperature is below a predetermined value.

19. The electrically commutated actuator and control system of claim 14, wherein the control circuit stores a predetermined phase shift corresponding to a predetermined d-axis component, and wherein the control circuit shifts the phase of the current on the at least one coil by the predetermined phase shift to introduce the predetermined d-axis component in response to receipt of the signal indicative of a request to dissipate heat in the at least one coil.

20. The electrically commutated actuator and control system of claim 14, comprising three of said at least one coil arranged in a three-phase configuration with respect to said shaft and said amplifier.

21. The electrically commutated actuator and control system of claim 14, wherein said control circuit defines a maximum total current in said at least one coil, and wherein when an aggregate of said q-axis component and said d-axis component exceeds said maximum total current, said control circuit decreases said d-axis component such that said aggregate does not exceed said maximum total current.

22. The electrically commutated actuator and control system of claim 14, wherein said second input carries information indicating the presence of a regeneration event.

23. The electrically commutated actuator and control system of claim 14, wherein:

the control circuit includes a processor configured to:

determining the power dissipated in the at least one coil,

the mechanical power on the rod is determined,

determining a power on a bus between the battery and the at least one coil based on the dissipated power and the mechanical power to produce an indication signal, an

Wherein the control circuit is configured to shift a phase of a current on the at least one coil to introduce the d-axis component when the indication signal corresponding to the comparison indicates a regenerative current.

24. Use of an electrically commutated actuator and control system according to any of claims 14-23 for actively suspending a device in a vehicle.