JP2011002082A - Drive device and speed command generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a control error caused by sliding generated on a rolling surface in a drive device which outputs a driving force of a motor via a transmission mechanism which transmits the driving force by friction of the rolling surface between an input rolling element and an output rolling element.SOLUTION: Load torque T transmitted by the transmission mechanism is calculated from an current I supplied to the motor, and a motor rotational speed ω1 (load torque calculation section 30). A slip ratio and a slip velocity slipω1 are determined from the calculated load torque T by using a previously determined relation between the load torque T and the slip ratio slip. The error caused by sliding can be reduced by adding thereof to the target speed command value.

Description

  The present invention relates to a drive device having a transmission mechanism for transmitting power by friction between an input rolling element and an output rolling element, and more particularly to speed control thereof.

  A transmission mechanism that converts the rotational speed on the input side and transmits it to the output side, such as a gear mechanism, is known. In the gear mechanism, the gear ratio is determined by the ratio of the number of teeth of the input side gear and the output side gear. Therefore, the transmission ratio is an integer ratio, that is, a discrete value, and there is a problem that the degree of freedom in design is low. If the rollers without the gear teeth are brought into contact with each other and rotation is transmitted by friction between the rollers, the radius of the roller can take a continuous value, and the transmission ratio can also be set freely. Further, it is possible to configure a transmission mechanism with less transmission error and no backlash compared with gear transmission.

  Patent Document 1 below discloses a friction transmission mechanism in which a sun gear, a ring gear, and a planetary pinion of a planetary gear mechanism are replaced with rollers.

JP-A-5-257536

  In the transmission mechanism using friction between rolling elements such as rollers as described above, slip occurs between the two rolling elements, and an error occurs in the rotation transmission.

  An object of this invention is to implement | achieve the rotational speed control which anticipated the error by the sliding of rolling elements.

  In the drive device according to the present invention, the slip of the rolling elements on the input side and the output side depends on the ratio (traction coefficient) between the force that presses the rolling elements and the force that transmits the rotation between the rolling elements. Is used to predict the slip that occurs and reflect this in speed control. The force that presses the rolling elements is treated as a fixed value, and slip is estimated from the force that transmits rotation.

  Specifically, the drive device includes a motor and a transmission mechanism that transmits the driving force of the motor between the input rolling element and the output rolling element by friction of the rolling surface, and is based on the speed command value. Current command means for calculating a current command value and supplying these command values to the motor, input-side speed obtaining means for obtaining the rotational speed of the input rolling element coupled to the motor output shaft, current command value and input Load torque calculating means for calculating the load torque of the motor based on the rotational speed of the rolling element; slip speed calculating means for calculating the slip speed generated in the transmission mechanism based on the load torque and the rotational speed of the input rolling element; Adding means for calculating the speed command value corrected by adding the slip speed to the target speed command.

  Further, the sliding speed calculating means has an oil temperature acquisition means for acquiring the temperature of the lubricating oil that lubricates the rolling surfaces of the input rolling element and the output rolling element, according to the acquired lubricating oil temperature. The sliding speed can be calculated.

  A driving device according to another aspect of the present invention outputs a driving force of a motor via a transmission mechanism that transmits a driving force by friction of a rolling surface between an input rolling member and an output rolling member. Further, it has a control unit for controlling the motor, and this control unit sets the rotation speed pattern of the output shaft of the transmission mechanism and the rotational inertia connected to the output side of the transmission mechanism. A setting unit; load torque calculating means for calculating a load torque of the motor from the set rotation speed pattern and rotation inertia; and a slip ratio calculating means for calculating a slip ratio generated in the transmission mechanism based on the load torque of the motor; A speed command value generating unit that obtains a rotational speed pattern of the input shaft of the transmission mechanism from a load torque of the motor, a slip ratio, and a rotational speed pattern of the output shaft, and generates a speed command value corresponding to the rotational speed pattern; In value And a drive unit for driving and controlling the motor I.

  Further, the slip ratio calculating means may acquire an assumed temperature of the lubricating oil for lubricating the rolling surfaces of the input rolling element and the output rolling element, and calculate the slip speed according to the temperature.

  A driving device according to still another aspect of the present invention provides a speed command for a motor that outputs a driving force via a transmission mechanism that transmits a driving force by friction of a rolling surface between the input rolling element and the output rolling element. A speed command generating device for generating a value, an operating condition setting unit for setting a rotational speed pattern of an output shaft of the transmission mechanism and a rotational inertia connected to an output side of the transmission mechanism, and the set rotational speed Load torque calculation means for calculating the load torque of the motor from the pattern and rotational inertia; slip ratio calculation means for determining the slip ratio generated in the transmission mechanism based on the load torque of the motor; load torque of the motor; slip ratio; A speed command generating unit that obtains the rotational speed pattern of the input shaft of the transmission mechanism from the rotational speed pattern of the output shaft and generates a speed command value corresponding to the rotational speed pattern.

  Since the control is performed in consideration of the slip between the rolling elements, the rotation transmission error is reduced.

It is a figure which shows schematic structure of the transmission mechanism by friction. It is a figure which shows the relationship between a traction coefficient and a slip ratio. It is a block diagram which shows schematic structure of a drive device. It is a figure which shows a simulation result. It is a block diagram which shows schematic structure of another drive device. It is a figure which shows the planetary roller type deceleration device which is an example of a transmission mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drive device according to the present invention includes a transmission mechanism that transmits rotation between the rotating bodies. At least one of the rotating bodies of the transmission mechanism contacts the other party so as to roll, and a force is transmitted by friction of the contacting portion. Therefore, the transmission mechanism according to the present invention does not include a transmission mechanism such as a clutch in which two rotating bodies are coupled together to transmit rotation. In order to distinguish between transmission mechanisms such as clutches, hereinafter, both the rotating body that makes contact with rolling and the rotating body that comes into contact will be described as rolling elements.

  FIG. 1 is a diagram illustrating a force acting between two rolling elements that perform rotation transmission. The two rolling elements 10 and 12 are rollers that rotate around parallel axes. The roller shown below is the driving roller 10, and the roller shown above is the driven roller 12. The driving roller 10 has a radius r1 and rotates at an angular velocity ω1. The driven roller 12 has a radius r2 and rotates at an angular velocity ω2. The two rollers 10 and 12 are pressed against each other by a pressing force Fn, and a lubricating oil 14 is interposed between them. In the common tangential direction of the two rollers, a force (hereinafter referred to as tangential force) Ft for transmitting rotation acts between the two rollers.

If there is no slip between the two rollers 10, 12,
r2 / r1 = ω1 / ω2 (= λ) (1)
Is established. λ is a gear ratio. Slip is the tangential speed difference at the contact point of the rollers 10, 12, i.e.
r1 × ω1 −r2 × ω2
Further, the slip ratio slip is defined by the following equation.
slip = (r1 × ω1−r2 × ω2) / (r1 × ω1)
= 1-λ (ω2 / ω1) (2)
The slip ratio slip is a ratio of the tangential force Ft and the pressing force Fn in the normal use region.
μ = Ft / Fn (3)
There is a linear relationship. As shown in FIG. 2, since the design specification is used below the maximum value of the traction coefficient μmax, the relationship between the slip rate slip and the traction coefficient μ is almost linear. Also, let C be the proportional coefficient of the linear range.
μ = C × slip (4)
This coefficient C varies depending on the temperature of the lubricating oil. Usually, the coefficient C takes a larger value when the temperature of the lubricating oil is lower.

If the transmission torque between the rollers 10 and 12 is T,
T = r1 x Ft (5)
If the equations (3) and (4) are substituted into the equation (5), the following equation is obtained.
T = C × slip × r1 × Fn
Or
slip = T / (C × r1 × Fn) (6)
It can be expressed.

  FIG. 3 is a block diagram illustrating a schematic configuration of a drive device 18 including a transmission mechanism 16 that transmits rotation between rolling elements. The drive device 18 includes a motor 20 that generates a driving force, a motor drive unit 22 that drives and controls the motor 20, and a transmission mechanism 16 that decelerates and outputs the output of the motor. The transmission mechanism 16 may be a mechanism that transmits rotation between the two rollers described in FIG. 1, for example. Hereinafter, this mechanism will be described as an example. Further, the transmission device 16 may increase the output of the motor, or may transmit at a constant speed.

  The output shaft of the motor 20 is connected to the driving roller 10 that is the input side of the transmission mechanism 16. The control of the motor 20 is executed according to a target speed command value that determines the rotation speed of the output shaft. The target speed command value is calculated according to a speed pattern in which the movement of the motor or a driven object driven by the motor via the transmission mechanism 16 is determined as a speed change. Based on this target speed command value, the current command unit 24 calculates a torque to be generated by the motor 20 and a current value to be supplied to the motor 20, and supplies the motor 20 as a current command value. The motor 20 includes a current supply unit that supplies a current according to the current command value to the coil, thereby driving the motor.

  The speed command value supplied to the current command unit 24 is obtained by subtracting the rotational speed of the output shaft of the motor 20, that is, the rotational speed ω1 of the driving roller 10 from the target speed command value. A rotation speed sensor 26 is provided on the output shaft of the motor 20, and an output value of this sensor is subtracted by an adder 28 to constitute a feedback system.

  Furthermore, the motor drive unit 22 has a configuration for dealing with slipping in the transmission mechanism 16. As shown in Expression (6), the slip ratio slip is determined by the transmission torque T transmitted by the transmission mechanism 16, the coefficient C, the radius r1 of the driving roller, and the pressing force Fn. The radius r1 and the pressing force Fn are fixed values, and the coefficient C varies depending on the temperature, but can be obtained in advance. Therefore, if the transmission torque T in Equation (6) can be obtained, the slip ratio can be calculated, and the amount of slip occurring at that time can be estimated. By controlling the motor 20 in consideration of the slip amount, an error due to the slip amount can be suppressed.

Specifically, the motor drive unit 22 includes a load torque calculation unit 30 that calculates a load torque and a slip speed calculation unit 32 that calculates a slip speed. Since the load torque is a torque applied to the output side of the transmission mechanism, this is the transmission torque T described above. Assuming that the load torque T is the output torque Tm of the motor, the rotational inertia of the rotating part from the motor rotor to the input side of the transmission mechanism is Im, and the mechanical loss torque Tl in the transmission mechanism 16
T = Tm−Im × β1−Tl (7)
It can be expressed as β1 is the angular acceleration of the driving roller 10 (β1 = (d / dt) ω1). Furthermore, if the current command value to the motor is I,
Tm = f (I) (8)
It can be expressed as. f is a function representing the relationship between the current of the motor and the output torque of the motor, and this is a function that can be obtained by performing a performance test on the motor used. From the equations (8) and (7), the following equation is obtained.
T = f (I) -Im * [beta] 1-Tl (9)
Further, when the formula (9) is substituted into the formula (6), the following formula is obtained.
slip = (f (I) -Im * [beta] 1-Tl) / (C * r1 * Fn) (10)

  In the load torque calculation unit 30, the load torque T is calculated based on Expression (9). The rotational inertia Im is a fixed value. On the other hand, the mechanical loss torque Tl can be roughly treated as a fixed value. Actually, it varies depending on the rotational speed, temperature, etc., and may be treated as a function of these parameters. The current command value I can be obtained from the output of the current command unit 24, and the angular acceleration β1 can be obtained by obtaining the rotational speed ω1 of the output shaft of the motor 20 from the rotational speed sensor 26 and differentiating it. The slip speed calculator 32 calculates the slip rate slip according to the equation (6), and further multiplies the slip rate by the rotational speed ω1 of the driving roller 10 to calculate the slip speed slip × ω1. This is added to the target speed command value by the adder 28. Equation (6) includes the coefficient C. The coefficient C is a function of the temperature of the lubricating oil as described above. However, the coefficient C may be treated as a fixed value if the lubricating oil temperature is stable during operation of the driving device 18. When handling the coefficient C as a function of temperature, the relationship between the lubricating oil temperature and the coefficient C is obtained in advance, a temperature sensor for detecting the temperature of the lubricating oil is provided, and the coefficient C is obtained from the oil temperature at that time. It's okay.

  As described above, the rotational speed ω1 of the motor output is fed back to the target speed command value, and the correction by the estimated slip speed slip × ω1 is performed to improve the control accuracy. FIG. 4 shows a simulation result of control for positioning to the target rotation angle. It can be understood that the position is almost set to the target value by correcting the slip amount.

FIG. 5 is a block diagram showing a schematic configuration of another driving apparatus 40 according to the present invention. The drive device 40 includes the motor 20, the transmission mechanism 16, and the current command unit 24 that are the same as those of the drive device 18. The current command unit 24 is included in the control unit 42, and the control unit 42 has a configuration that further generates a target speed command value to be supplied to the current command unit 24 in consideration of slippage of the transmission mechanism 16. When the equation (2) is transformed, the following equation is obtained.
ω1 = λ × ω2 / (1-slip) (11)

  This indicates that when the control target of the angular velocity ω2 of the output shaft of the transmission mechanism 16 can be set in advance, if the slip ratio slip can be estimated, the control target of the angular velocity ω1 of the input shaft can be set in consideration of the slip. . For example, the robot arm is programmed in advance to perform a predetermined operation, and the programmed operation defines a control target. In order to perform this operation, a control target, that is, a target speed command value is set for each motor that drives the movable part of each part of the arm. At this time, as described above, the target speed command value can be set in consideration of the slip. In the following description, it is assumed that the target rotational speed pattern of the output shaft of the transmission mechanism 16 is ω2ref, and the rotational speed pattern of the input shaft calculated to realize this pattern is ω1ref. If the rotational speed pattern ω2ref of the output shaft is set and the rotational inertia Io of the controlled object is known, the load torque of the motor can be obtained in advance and the slip ratio can be calculated. Thereby, the input shaft rotational speed pattern ω1ref considering the slip ratio is obtained.

For this purpose, the control unit 42 of the drive device 40 includes a rotation speed pattern ω2ref of the output shaft, a setting unit 44 that sets the rotation inertia of the configuration to be controlled, and a load torque pre-calculation unit that calculates the load torque from these set values. 46, a slip ratio pre-calculating section 48 for calculating a slip ratio from the load torque, and an input shaft speed pattern calculating section 50 for calculating the rotational speed pattern ω1ref of the input shaft from the set value and the calculated value. When equation (11) is rewritten using the rotational speed patterns ω1ref and ω2ref that are the control targets of the input shaft and the output shaft, the following equation is obtained.
ω1ref = λ × ω2ref / (1-slip) (12)

If the rotational inertia on the output side of the transmission mechanism 16 is Io, the load torque is To, and the mechanical loss torque is Tol,
To = Io × β2ref + Tol (13)
It can be expressed as β2ref is the angular acceleration of the driving roller 12 which is the output side of the transmission mechanism 16 (β2ref = (d / dt) ω2ref). Furthermore, the input torque T of the transmission device 16 can be expressed by the following equation, where η is the efficiency of the transmission device 16.
T = To / (λ × η) = (Io × β2ref + Tol) / (λ × η) (14)
Substituting equations (6) and (14) into equation (12) yields the following equation.

  In the setting unit 44, the output shaft rotational speed pattern ω2ref to be realized is set, and the output side rotational inertia Io is set. The mechanical loss torque Tol can be handled as a fixed value. More strictly, it is necessary to change according to the rotation speed and torque. In the load torque pre-calculation unit 46, the load torque To is calculated in advance before actually controlling according to the equation (13). The slip ratio pre-calculation unit 48 calculates the slip ratio slip by substituting Expression (14) into Expression (6). The input shaft speed pattern calculation unit 50 calculates the input shaft rotation speed pattern ω1ref by applying the slip ratio slip to the equation (12). The above calculation of the rotational speed pattern ω1ref of the input shaft is summarized as the above equation (15).

  The rotational speed pattern ω1ref of the input shaft obtained by the control unit 42 of the drive device 40 can also be used as a target speed command value for the drive device 18.

  FIG. 6 shows a planetary roller type reduction device 60 as an example of a transmission mechanism. The speed reducer 60 has two sets of planetary roller mechanisms, an input side planetary roller mechanism 62 and an output side planetary roller mechanism 64. The sun roller 62 </ b> S of the input side planetary roller mechanism 62 is an input shaft of the speed reduction device 60, and the ring roller 64 </ b> R of the output side planetary roller mechanism 64 is coupled to the output shaft of the speed reduction mechanism 60. The planetary rollers 62P and 64P of the two planetary roller mechanisms 62 and 64 have different radii, but are integrated and supported rotatably by the planetary carrier 62C. In this speed reduction device 60, there are two rolling contact points. However, the slip is detected as a difference in rotational speed between the input shaft and the output shaft of the speed reduction device 60, and the relationship between the total slip of the two contact points and the traction coefficient. Can be described. Therefore, it is possible to calculate the slip ratio and the like as in the transmission between the two rollers 10 and 12 described above.

  DESCRIPTION OF SYMBOLS 10 Drive side roller (input rolling element), 12 Driven side roller (output rolling element), 16 Transmission mechanism, 18 Drive apparatus, 20 Motor, 22 Motor drive part, 24 Current command part, 26 Rotational speed sensor, 28 Adder , 30 load torque calculation unit, 32 slip speed calculation unit, 40 drive unit, 42 control unit, 44 setting unit, 46 load torque pre-calculation unit, 48 slip rate pre-calculation unit, 50 input shaft speed pattern calculation unit.

Claims (5)

A driving device including a motor and a transmission mechanism that transmits the driving force of the motor between the input rolling element and the output rolling element by friction of a rolling surface;
A current command value is calculated based on the speed command value, and current command means for supplying the command value to the motor;
Input-side speed acquisition means for acquiring the rotational speed of the input rolling element coupled to the output shaft of the motor;
Load torque calculating means for calculating the load torque of the motor based on the current command value and the rotational speed of the input rolling element;
A slip speed calculating means for calculating a slip speed generated in the transmission mechanism based on the load torque and the rotational speed of the input rolling element;
Adding means for calculating the speed command value corrected by adding the slip speed to the target speed command;
A driving device. The drive device according to claim 1,
Oil temperature acquisition means for acquiring the temperature of the lubricating oil that lubricates the rolling surfaces of the input rolling element and the output rolling element,
In the slip speed calculating means, the slip speed is calculated according to the acquired temperature of the lubricating oil.
Drive device. A driving device that outputs a driving force of a motor via a transmission mechanism that transmits a driving force by friction of a rolling surface between an input rolling element and an output rolling element,
Having a control unit for controlling the motor,
The controller is
An operating condition setting unit for setting the rotational speed pattern of the output shaft of the transmission mechanism and the rotational inertia connected to the output side of the transmission mechanism;
Load torque calculation means for calculating a load torque of the motor from the set rotation speed pattern and rotation inertia;
A slip ratio calculating means for determining a slip ratio generated in the transmission mechanism based on a load torque of the motor;
A speed command value generation unit that determines a rotation speed pattern of the input shaft of the transmission mechanism from the slip rate and the rotation speed pattern of the output shaft, and generates a speed command value corresponding to the rotation speed pattern;
A drive unit that drives and controls the motor according to the speed command value;
A driving device. The drive device according to claim 3,
The slip ratio calculating means acquires an assumed temperature of the lubricating oil that lubricates the rolling surfaces of the input rolling element and the output rolling element, and calculates a slip speed according to the temperature.
Drive device. A speed command generation device that generates a speed command value of a motor that outputs a driving force via a transmission mechanism that transmits a driving force by friction of a rolling surface between an input rolling element and an output rolling element,
An operating condition setting unit for setting the rotational speed pattern of the output shaft of the transmission mechanism and the rotational inertia connected to the output side of the transmission mechanism;
Load torque calculation means for calculating a load torque of the motor from the set rotation speed pattern and rotation inertia;
A slip ratio calculating means for determining a slip ratio generated in the transmission mechanism based on a load torque of the motor;
A speed command generation unit for obtaining a rotational speed pattern of the input shaft of the transmission mechanism from a load torque of the motor, a slip ratio, and a rotational speed pattern of the output shaft, and generating a speed command value corresponding to the rotational speed pattern;
Having
Speed command generator.

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