DE10226988A1 - Determining shaft angle from 3 single turn angle sensor signals involves computing virtual intermediate parameters, determining number of revolutions, adding to first sensor signal plus 360 degrees - Google Patents

Abstract

The method involves computing a first virtual intermediate parameter from the angle signals of first and second angle sensors and a constant, computing a second virtual intermediate parameter from the first virtual intermediate parameter and the angle signal of a first pinion sensor, determining the number of revolutions and adding to the first angle sensor signal plus 360 degrees. The method involves computing a first virtual intermediate parameter phioS as (n + 1*deltaVA1 + n*deltaVA2 + 25*k*360 degrees)/312, where deltaVA1 and deltaVA2 are angle signals of first and second angle sensors (41,43) and k is a constant, computing a second virtual intermediate parameter as (M*phioS + m + n*deltaRi1 + 9*k*360 degrees)/40, where deltaRi1 is the angle signal of a first pinion sensor, determining the number of revolutions and adding to the first angle sensor signal plus 360 degrees.

Description

The invention relates to a method for determining the angle of rotation of a shaft from the angle signal a first angle sensor and the angle signal of a second angle sensor, wherein the first angle sensor and the second angle sensor rigid with the shaft are coupled, the gear ratio between first angle sensor and shaft on the one hand and the transmission ratio between second angle sensor and shaft on the other hand different from each other and with one coupled to the shaft via a torsion bar Pinion angle sensor.

Such arrangements are used, for example, in steer-by-wire steering systems as a steering actuator or steering wheel actuator with two redundant electric motors used. However, the invention is not in this area of application limited.

To the manufacturing costs of the angle sensors to minimize, so-called single-turn sensors are usually used a measuring range from 0 ° to Have 360 °. If this sensor is rotated by an angle> 360 ° it starts again at 0 ° This means that, for example, the output signal of such an angle sensor at a Rotation by 180 ° exactly is the same as for a rotation of 540 °. Because usually in motor vehicles the steering column turned from stop to stop by four turns, corresponding to 1,440 ° , it is necessary to clearly determine the angle of rotation the steering column to be able to make. This is done according to the so-called Nonius method, by using the Signals from the first angle sensor and the second angle sensor, due to the different gear ratios differ from each other, as well as the signal of the coupled with the shaft Pinion angle sensor determines the angle of rotation of the steering column.

Determining the angle of rotation of the steering column we you. a. difficult because the first angle sensor and the second angle sensor their signals are not always on at the same time control unit or send an evaluation unit and usually the clock frequency, with which the first angle sensor, the second angle sensor, the pinion angle sensor and the control unit operated, is not the same. Therefore, from the first angle sensor, second angle sensor and pinion angle sensor present in the control unit Signals do not immediately lead to a clear determination of the angle of rotation the steering column be used directly.

With the method according to the invention however, it is possible the signals of the first angle sensor, the second angle sensor and the pinion angle sensor despite the difficulties mentioned to evaluate clearly and easily, so that the determination the angle of rotation of the steering column even with different clock frequencies and / or time shifts between the input of the incoming sensors Signals can be made.

This process is based on the three process steps listed below:
- Calculate a first virtual intermediate _variable (φ _αS ) according to the formula φ αS = (n + 1 ∙ δ V A 1 + n ∙ δ V A 2 + 25 ∙ k ∙ 360 °) / 312
With:
δ _{V A 1} : angle signal of the first angle sensor
δ _{V A 2} : angle signal of the second angle sensor
k: constant; for four steering wheel turns from steering stop to steering stop, corresponding to 1440 °, the following applies to k:
k = (4 ∙ φ αS - 5 ∙ δ V A 1 2 ) / 360 ° ,

- Calculate a second virtual intermediate variable (φges) according to the formula φ ges = (m ∙ φ αS + m + 1 ∙ δ Ri1 + 9 ∙ k ∙ 360 °) / 40
With:
m: constant
δ _Ri1 : Angle signal from the pinion angle sensor
k: constant

Determine the number of revolutions (n) and add the angle signal (δ _{V A 1} ) of a first angle sensor to the product of the number of revolutions (n) and 360 °.

Advantages of invention

The method according to the invention is simple to carry out, only requires a low computing power and enables despite different Clock frequencies with which the sensors mentioned are scanned and / or temporal shifts between the input of the signals a clear and reliable Determination of the angle of rotation of the steering column. Here is the procedure robust against interference and makes little demands on the hardware.

In a variant of the method according to the invention it is intended that the number of revolutions of the shaft of the steering column an integer division of the second virtual intermediate size 360 ° is done and the remainder of the division is lost. This makes it easy the number of revolutions of the shaft used for the unambiguous determination the angle of rotation of the steering column is determined.

Alternatively, the number of revolutions of the steering column can also be determined using the following procedure:
- _Forming a difference (Δ _{δV A 1} ) of an angle signal (δ _{V A 1} (t)) of the first angle sensor at time t and an angle signal (δ V A 1 (t - 1)) the first angle sensor at time t - 1,
- Increase the number (n) of revolutions of the shaft when the difference (Δ .DELTA.V A 1 )> 180 ° is
- Decrease the number (n) of revolutions of the shaft if the difference (Δ .DELTA.V A 1 ) <-180 ° is or
- Maintain the number (n) of revolutions of the shaft when the amount of the difference (☐Δ .DELTA.V A 1 ☐) ≤ 180 ° is.

This procedure allows it to continue update the number of turns of the steering column. there the effect is exploited, that the driver of a vehicle in the period between two scans of the first angle sensor is not the steering column of the vehicle can quickly turn that the output signal of the first angle sensor or of the second angle sensor at time t from the angle signal at time t - 1 by more than 90 ° to differs by a maximum of 120 °. Therefore it is possible to be able to say with certainty that if the difference of an angle signal of the first angle sensor or the second angle sensor at time t and an angle signal of the first angle sensor or the second angle sensor at the time t - 1> 180 °, that steering column was turned one turn. In the same way you can say that the number of revolutions of the shaft will be decreased by 1 can if the above Difference is less than -180 °. In this case, the Number of turns of the steering column be decreased by 1. In all other cases, namely when Amount of the above Difference is ≤ 180 °, can the number of turns of the steering column remain the same. If so to the number of turns of the steering column multiplied by 360 ° or the currently determined angle of the pinion angle sensor is added, the angle of rotation of the steering column has been clearly determined.

To further simplify this The method can also be the difference of an angle signal of the first Angle sensor or the second angle sensor at time t and an angle signal of the first angle sensor or the second angle sensor at the time t - 1 be normalized by dividing by 360 and the normalized Difference to be rounded. The result of this rounding can be –1, 0 or +1. This result becomes the current number of revolutions the shaft or the steering column added.

It has been put into practical trials found to be advantageous when initializing the number of the revolutions of the shaft the first-mentioned method, which is based on an integer division of the second virtual intermediate variable and after initialization, the procedure is applied, which is based on the difference of an angle signal at time t and t - 1 builds.

The method according to the invention can be particularly advantageous to determine the angle of rotation of a steering gear of a vehicle steering system, in particular a steer-by-wire steering, or a steering wheel actuator steer-by-wire steering.

Other advantages and beneficial Embodiments of the invention are the following drawing, their description and the claims can be found.

drawing

Show it:

• 1 a schematic representation of a steer-by-wire steering,
• 2 1 shows a schematic representation of a steering actuator,
• 3 a block diagram of the control of the steering actuator and
• 4 a representation of the inventive method for calculating the first and second virtual intermediate variable.
• 5 shows the further processing of the second virtual intermediate size and
• 6 shows a section of the course of the calculated quantities depending on the angle of rotation of the steering column.

description of the embodiments

1 shows a schematic representation of an embodiment of a steer-by-wire steering system with a hydraulic power steering gear.

A steering wheel 1 serves as a steering handle and is on a steering column 3 attached, which is mounted in the chassis of a vehicle, not shown. On the steering column 3 is a steering wheel actuator 5 arranged.

In the 1 Steered wheels, not shown, are via a tie rod 9 adjusted. The tie rod is operated 9 in the embodiment according to 1 via a known hydraulic power steering gear 11 , The hydraulic power steering gear 11 has one in 1 Rack, not shown, on the tie rods 9 acts, and which of a pinion 13 is driven. Above the pinion 13 and rotatably connected to this is a torsion bar valve with a torsion bar 15 to control the servo support of the hydraulic power steering gear 11 arranged. The torsion bar valve controls the flow rate of a servo pump 17 in a double-acting working cylinder arranged parallel to the rack 19 ,

In contrast to conventional steering systems, the hydraulic power steering gear 11 to 1 in steer-by-wire operation as in 1 is shown by a steering actuator 21 and not directly from the steering column 3 actuated. In 1 is a clutch 23 the steering column 3 shown in the open state. With the clutch open 23 there is no mechanical connection between the steering wheel 1 over the steering column 3 to the hydraulic power steering gear 11 , So there is no mechanical connection from the steering wheel 1 to the steered wheels, not shown.

The steering actuator 21 is controlled by a control unit (not shown) in such a way that it fulfills the driver's steering request, which is caused by turning the steering wheel 1 expresses, translates into a steering movement of the steered wheels. For this, it is necessary, on the one hand, that both the angle of rotation of the steering wheel 1 connected part of the steering column 3 as well as the position of the tie rod 9 or the angle of rotation of the pinion 13 be clearly recorded. In the steer-by-wire steering systems of the prior art, this is done by angle sensors.

The steering actuator 21 consists essentially of a first electric motor 27 and a second electric motor 29 , On the motor shaft of the first electric motor 27 and the second electric motor 29 is a pinion each 35 and 37 educated. The pinion 35 and 37 are engaged with a gear wheel 39 , which rotatably with the pinion 13 opposite end of the torsion bar 15 connected is. About the torsion bar 15 every rotation of the gear wheel 39 on the pinion 13 transfer. The torsion bar 15 takes over the function of the output shaft in this embodiment. The pinion 13 again, as already mentioned, is engaged with a rack, not shown.

The first electric motor 27 has a first angle sensor 41 on. The second electric motor 29 has a second angle sensor 43 on. The first and second angle sensor 41 and 43 are designed as so-called single-turn sensors, ie they can determine the rotational position of the motor shafts of the first and second electric motors 27 and 29 only specify clearly in an angular range between 0 ° and 360 °. Several revolutions of the first and second electric motor 27 and 29 can from the first angle sensor 41 and from the second angle sensor 43 cannot be distinguished.

Therefore, the number of teeth on the pinion gives way 35 and the number of teeth of the pinion 37 from each other, so that the angle of rotation> 360 ° of the gear wheel 39 and thus also the torsion bar 15 or the pinion 13 clearly from the signals of the first angle sensor 41 , of the second angle sensor 43 and one on the pinion 13 arranged pinion angle sensor 45 can be determined.

For this reason, when using a steering actuator 21 by evaluating the signals from the first and second angle sensors according to the invention 41 and 43 and pinion angle sensor 45 on the use of an expensive multi-turn sensor in the area of the torsion bar valve 15 , the pinion 13 or, if the actuator is used as a steering handle actuator, the steering column 3 to be dispensed with.

A control unit 47 receives the signals from the three sensors mentioned via dashed lines. The signal from the first angle sensor 41 is denoted by δ _{V A 1} , the signal of the second angle sensor 43 denoted by δ _{V A 2} and the signal of the pinion angle sensor 45 is _denoted by δ _Ri1 . Based on this information, the control unit can 47 the angle of the steering column 3 clearly determine and if necessary the first electric motor 27 and the second electric motor 29 control so that the angle of rotation of the torsion bar 15 corresponds to a predetermined target value. The control of the first electric motor 27 and the second electric motor 29 is in 1 not shown. These motors can also be controlled as a function of other parameters, here collectively designated 49.

In 2 is the steering actuator 21 shown schematically. From this illustration it is clear that the gear wheel 39 , which rotates with the steering column 3 (not shown) on the one hand and with the torsion bar 15 on the other hand is connected by a first pinion 35 and a second sprocket 37 is driven. The first electric motor 27 as well as the first angle sensor 41 are in 2 not shown. The same applies to the second electric motor 29 and the second angle sensor 43 (please refer 1 ). However, it is the case that the first angle sensor 41 the angle of rotation of the first electric motor, not shown 27 or the first pinion 35 measures. The same applies in a corresponding manner to the second angle sensor 43 , In the 2 are examples of an angle 6vai on the first pinion 35 entered. This angle δ _{V A 1} is from the first angle sensor 41 (not shown) recorded. The second angle sensor 43 (not shown) correspondingly detects a rotation angle δ _{V A 2 of} the second pinion 37 , Because of the rigid coupling between the first pinion 35 and second pinion 37 with the gear wheel 39 can from the angles of rotation δ _{V A 1} and δ _{V A 2} an angle of rotation δ _{V A 12} on the gear wheel 39 be calculated.

The number of teeth Z _{2 of} the second pinion 37 is equal to p. The number of teeth Z _{1 of} the first pinion 35 is increased by 1 compared to the number of teeth of the second pinion (Z ₁ = Z ₂ + 1). The number of teeth Z _{3 of} the gear wheel 39 is equal to m. Because of the different number of teeth of the first pinion 35 , second pinion 37 and gear wheel 39 the angles δ _{V A 1} , δ _{V A 2} and δ _{V A 1 2} are different from one another. These differences are exploited to work on the first sprocket despite the use of single-turn sensors 35 and on the second sprocket 37 the angle of rotation of the steering column or the torsion bar 15 to be clearly determined.

The angle δ _{V A 1 2} is in accordance with the embodiment 2 not directly on the gear wheel 39 detected, but by the pinion angle sensor 45 on the pinion 13 (not shown; see here 1 ) detected. The one from the pinion angle sensor 45 captured angle is in 2 and hereinafter referred to as δ _Ri1 . Because of the ability of the torsion bar 15 to twist under load, the angle δ _Ri1 does not exactly correspond to the angle δ _{V A 12} . As it is for precise control of the position of the steered wheels of the vehicle on the position of the pinion 13 or the rack, which the tie rod 9 actuated (see 1 ) arrives it makes sense to set the rotation angle δ _{Ri1 of} the pinion 13 to capture directly. The torsion of the torsion bar 15 caused differences between the pinion angle δ _Ri1 and the angle of rotation δ _{V A 12 of} the gear _wheel 39 are equalized or eliminated with the method according to the invention.

Below are the names introduced above for the various signals of the angle sensors 41 . 43 and 45 maintained.

In 3 is the control concept of the steering actuator 21 shown in simplified form as a block diagram. The input variable of this control loop is one from the steering wheel 1 on the steering column 3 transferred driver steering request δ _LR . The input variable δ _LR is the angle signal of an in 1 Steering wheel angle sensor, not shown, and is an angle preparation 53 and an addition point 51 fed. There, an output variable δ _{V A 2 of} the control loop with a negative sign is added to the input variable δ _LR .

The output variable of a Robust Position Controller RPC, to which the variable δ _LR - δ _{V A 2 is} applied, is a voltage U _{S Q} in the rotor-fixed coordinate system. This voltage U _SQ can, if necessary, be influenced by a Friction Force Compensator FFC if permanent vibrations occur. The sum of the voltages output by the Robust Position Controller RPC and the Friction Force Controller FFC is used as an input variable in a Constraint Torque Controller CTC. The Constraint Torque Controller CTC distributes the voltage from the torque control to a space vector modulation RZM. This determines the switching times for controlling the steering actuator 21 in an inverter (not shown). In addition to the voltages, the angle signal δ _{V A 1 of} the first angle sensor is used for this purpose 41 and the angle signal δ _{V A 2 of} the second angle sensor 43 related.

The steering actuator becomes the output variables of the space vector modulation RZM 21 driven. The result of the control of the steering actuator 21 The resulting angle signals δ _{V A 1} , δ _{V A 2} and δ _Ri1 are read in via a CAN bus and sent to the angle _preparation 53 transmitted. With the aid of the method according to the invention, these individual single-turn angle signals become the actual value of the stator 39 calculated. The actual value δ _{V A 1 of} the stator 39 can be between –720 ° and + 720 °, corresponding to four full steering wheel rotations. This allows the absolute position of the steering wheel actuator 21 be clearly determined.

Since the known from the Nonius principle calculated angle information very sensitive to interference and therefore for position control, especially in the area of steer-by-wire steering, does not reliable is enough the above Angle signals are processed according to the inventive method.

Basically, the vernier principle allows the determination of an angle of rotation on a gear by measuring the angle on two smaller gears with different numbers of teeth. This requirement is with the steering actuator 21 given (see 2 ). The angle sensors 41 and 43 each generate an angle signal in a range from -180 ° to + 180 °, corresponding to one revolution of the first pinion 35 and the second pinion 37. In the selected application example of a steer-by-wire steering system, the number of teeth Z ₁ , Z ₂ and Z _{3 of} the first pinion 35 , the second pinion 37 and the gear wheel 39 chosen such that an absolute angle of 0 ° to 1,440 ° can be clearly determined in two calculation stages using the method according to the invention. The torsion of the torsion bar 15 (please refer 1 and 2 ) has not been taken into account in the description of the method according to the invention for simplification.

Based on 4 it becomes clear that from the measured input variables δ _{V A 1} , δ _{V A 2} in a first calculation stage a first virtual intermediate variable φ _{αS is} calculated according to the following formula: φ αS = (n + 1 ∙ δ V A 1 + n ∙ δ V A 2 + 25 ∙ k ∙ 360 °) / 312 ,

With the aid of this first virtual intermediate variable φ _αS and the pinion angle δ _Ri1 , a second virtual intermediate variable _φges is calculated in a second calculation step according to the following formula: φ ges = mφ αS + m + 1 ∙ δ Ri1 + 9 ∙ k ∙ 360 °) / 40 ,

The further procedure for determining the actual value δ _{V A 1 of} the stator 39 from the input variables mentioned is based on the 5 explained. When the method according to the invention is carried out for the first time, there is first an initialization of a counter 55 required. The counter 55 has the task of determining the number n of revolutions of the steering column. As already mentioned, it is assumed that the steer-by-wire steering system presented as an example can be turned from stop to stop with four turns of the steering column. This means that the number n can be between 1 and 4. The center position of the steering is therefore at the end of the second and before the start of the third turn.

To initialize the counter 55 the second virtual intermediate variable φ _{tot is} normalized to the number of revolutions by an integer division of the second virtual intermediate variable by 360 °. The remainder of the division is lost. With this variable n, hereinafter referred to as the number of revolutions of the steering column, the counter 55 initialized. In 5 this operating state is shown. Then the number n is multiplied by 360 ° and the angle signal δ _{V A 1 of} the first angle sensor 41 added. The result is the desired actual value δ _{V A 1 2 of} the stator 39 , or the pinion 13 ,

As soon as the counter is initialized 55 has taken place, an alternative method is used to determine the number n of revolutions of the steering column. This method uses the angle signal δ _{V A 1 of} the first angle sensor 1 and subtracts a quantity from this signal by a Division of the angle signal δ _{V A 1} with a size Z is formed. The size Z is equal to the number of teeth z _{1 of} the first pinion 35 ,

Then, in a jump detection Δ, the angle signal δ _{V A 1 is divided} by 360 ° and then rounded. This also gives the number n of revolutions of the steering column. With the jump detection Δ, the effect is exploited that the steering wheel 1 can only be rotated by the driver at a certain speed. This speed of rotation is so low that between two scans of the first angle sensor 41 the difference of the angle signal δ _{V A 1 of} the first angle sensor 41 cannot be greater than 90 °. The following procedure is therefore carried out in the jump detection Δ:
- _Forming a difference (Δ _{δV A 1} ) of an angle signal (δ _{V A 1} (t)) of the first angle sensor at the time t and an angle signal (δ _{V A 1} (t - 1)) of the first angle sensor at the time t - 1,
Increasing the number (n) of revolutions of the shaft if the difference (Δ _{δV A 1} ) is> 180 °,
- Decreasing the number (n) of revolutions of the shaft if the difference (Δδ _{V A 1} ) is <-180 ° or
- Maintaining the number (n) of revolutions of the shaft when the amount of the difference (| Δ _{δV A 1} |) is <180 °.

In this procedure the jump detection is thus a safety factor of 2 is available.

Alternatively, the difference A _{δV A 1} can also be normalized by dividing by 360 and this normalized difference Δ _{δV A 1,} rounded off. The result of the rounding is added to the number n of revolutions of the shaft. This alternative determination of the number n is made by the counter 55 applied after initialization. In 5 this is by a dashed line between the. Input of the counter 55 and its output is shown. The further procedure is carried out in the same way as described above.

In 6 the course of the variables described above is shown in diagram form. The relationships described above can be read from them.

The method according to the invention allows simple single-turn angle sensors to be used to determine the angle of rotation of a shaft that is not sensitive to interference, even if the various angle sensors 41 . 43 and 45 can be sampled at different sampling rates at different times. This makes it possible to use simple components without having to compromise on the security of the rotation angle determination. The clock frequency of the control unit 47 (please refer 1 ), in which the determination of the angle of rotation δ _{V A 12} can be integrated according to the method according to the invention, can be different from the sampling rate of the angle sensors mentioned.

Claims (7)

Method for determining an angle of rotation (δ _{V A 12} ) of a shaft ( 3 ) from the angle signal (δ _{V A 1} ) of a first angle sensor ( 41 ) and the angle signal (δ _{V A 2} ) of a second angle sensor ( 43 ), the first angle sensor ( 41 ) and the second angle sensor ( 43 ) rigid with the shaft ( 3 ) are coupled, the transmission ratio between the first angle sensor ( 41 ) and wave ( 3 ) on the one hand and the transmission ratio between the second angle sensor ( 43 ) and wave ( 3 ) on the other hand are different from each other, and with one with the shaft ( 3 ) coupled pinion angle sensor ( 95 ), characterized by the following process steps: - Calculating a first virtual intermediate _variable (φ _αS ) according to the formula φ αS = (n + 1 ∙ δ V A 1 + n ∙ δ V A 2 + 25 ∙ k ∙ 360 °) / 312 With. δ _{V A 1} : angle signal of the first angle sensor δ _{V A 2} : angle signal of the second angle sensor k: constant - calculating a second virtual intermediate variable (φ _tot ) according to the formula φ ges = (m ∙ φ αS + m + 1 ∙ δ Ri1 + 9 ∙ k ∙ 360 °) / 40 With. m: constant δ _Ri : Angle signal of the first pinion angle sensor k: Constant - determining the number of revolutions (n) and adding the angle signal (δ _{V A 1} ) of a first angle sensor ( 41 ) to the product of the number of revolutions (n) and 360 °. A method according to claim 1, characterized in that the number (n) of revolutions of the shaft ( 3 ) by an integer division of the second virtual intermediate variable (φ _tot ) by 360 °. A method according to claim 1, characterized in that the number (n) of revolutions of the shaft ( 3 ) is determined using the following method: - _Forming a difference (Δ _{δV A 1} ) of an angle signal (δ _{V A 1} (t)) of the first angle sensor at time t and an angle signal (δ _{V A 1} (t - 1 )) of the first angle sensor at time t - 1, - increasing the number (n) of revolutions of the shaft ( 3 ), if the difference (Δ _{δV A 1} )> 180 °, - lowering the number (n) of revolutions of the shaft ( 3 ) if the difference (Δ _{δV A 1} ) is <–180 ° or - maintaining the number (n) of revolutions of the shaft ( 3 ) if the amount of the difference (☐Δ _{δV A 2} ☐) is <180 °. A method according to claim 3, characterized in that the difference (Δ _{δV A 1} ) is normalized by division by 360, that the normalized difference (Δ _{δV A 1 , norm} ) is rounded and the result of the rounding to the number (n) of Revolutions of the shaft ( 3 ) is added. Method according to one of the preceding claims, characterized characterized that the procedure for initializing the number (s) performed according to claim 2 and that after initialization, the procedure according to the claim 3 is applied. Method according to one of the preceding claims, characterized characterized that the method of determining the angle of rotation of a steering gear of a vehicle steering system, in particular a steer-by-wire steering system becomes. Method according to one of the preceding claims, characterized in that the method for determining the angle of rotation of a steering wheel actuator ( 21 ) Steerby wire steering is used.