JP2005284599A - Method for controlling position and position control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position control device in which a response of a load is non-vibratory, its settling time is short and the device is robust in the parameter variation of the load. <P>SOLUTION: In the position control device, a load 400 is provided with a detection part A500 (acceleration sensor). A proportional integral signal of an acceleration signal for the load 4 which is detected by the acceleration sensor is negatively fed back to a driving force command to a motor 300. Then a proportional signal or a proportional integral signal for the motor 300 is negatively fed back to the driving force command. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to position control of machine tools, industrial robots, positioning devices, and the like.

  Referring to FIG. 1, there is shown a functional block diagram of an example of a prior art semi-closed loop position control device (see, for example, Patent Document 1 and Non-Patent Document 1). The purpose of the control is to make the load position respond according to the command. Proportional (P) control of the motor position of the mechanical system that can be approximated to a two-inertia system (system in which the motor and load are coupled by a spring and a damper) and proportional integral (PI) control of the motor speed are performed.

  In FIG. 1, the command unit 100 sends a driving force command for the motor 300 to the control unit 200, and the control unit 200 controls the motor 300 based on this command. The detection unit 500 (position sensor and speed sensor) monitors the position and speed of the motor 300, and feeds this back to the control unit 200 to form a closed loop of position and speed.

  Referring to FIG. 2, a specific control block diagram of this semi-closed loop position control device is shown (used in the following simulation). The shaded blocks (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) in FIG. 2 are the two inertial systems to be controlled (most of the controlled objects that cause mechanical vibrations are It is represented by a block diagram).

  In FIG. 2, 1 is the reciprocal of the mass of the motor (MM is the mass of the motor), 2 is the integral characteristic from the motor acceleration to the motor speed (physical dynamic characteristic, s is a symbol of Laplace transform), 3 is the motor speed Integral characteristics to motor position (physical dynamic characteristics), 4 is the reciprocal of the load mass (LM is the load mass), 5 is the integral characteristic from load acceleration to load speed (physical dynamic characteristics), 6 is Integral characteristic (physical dynamic characteristic) from load speed to load position, 7 is an adder / subtracter, 8 is a stiffness between a motor and a load (Ks is a spring constant), and 9 is a damper (D Is a damping gain), and 10 is an adder.

  Here, the output 3 is a motor position signal negatively fed back to the adder / subtractor 14, and the output 2 is a motor speed signal fed back to the adder / subtractor 28. The position signal of the motor that is negatively fed back to the adder / subtractor 14 is passed to a position proportional controller 27 (Kp is a proportional gain). The motor speed signal negatively fed back to the adder / subtractor 28 is passed to a speed proportional controller 29 (Kv is a speed proportional gain) and a speed integral controller 30 (Ti is an integration time). These negative feedback signals, together with the driving force command output from the command generator 13, are a proportional device 18 (Km is a proportional gain) that compensates for the motor mass, and a delay element 19 (Ta) that approximates the dynamic characteristics of the current amplifier and the motor. Is passed through a time constant) and output to a two-inertia system. Note that 31 is an adder, 32 is an adder, and 11 is an adder / subtracter.

20 and 21 are load disturbance force generators. In the following simulation, 20 generates a load disturbance force that rises in steps from zero to 100 N at t = 0.6, and 21 represents t = At 0.7, a load disturbance force falling from 100 N to zero is generated stepwise. Reference numeral 22 denotes a position recorder, which records the position of the motor as the output of 3 and the position of the load as the output of 6.
JP 11-31015 A Oishi Kiyoshi, “One-degree-of-freedom motion control”, Measurement and Control, Vol. 39, No. 10, October 10, 2001, p. 608-613

  The problems of the prior art position control device are as follows.

First, even if the motor position and the motor speed are fed back to improve the response of the motor, the response of the final target load position does not improve directly. In FIG. 2, Kp = 200 s ⁻¹ , Kv = 300 s ⁻¹ , Ti = 0.001 s, Km = 10 Ns / m, Ta = 0.001 s, MM = 10 kg, LM = 10 kg, Ks = 4000 N / m, D = 15 Ns / m is set, a step of 1 mm is given as a position command at time t = 0, and a force disturbance is stepped from zero to 100 N at t = 0.6, and 100 N at t = 0.7. The response was simulated by adding a step that falls from zero to zero. FIG. 3 shows the response of the motor position at this time, and FIG. 4 shows the response of the load position.

The motor response is fast and the position deviation is small. However, the load response is greatly oscillated with respect to the position step command, and the damping of the oscillation is slow. Thus, the response of the motor and the load are completely different. This tendency becomes stronger as Kp, Kv, and Ti ⁻¹ are increased and the motor response is increased.

  Second, it is not robust to load parameters. Of the above parameters, the response was simulated when only the load mass (LM) was doubled and the others were set exactly the same. FIG. 5 shows the response of the motor position at this time, and FIG. 6 shows the response of the load position. The motor response (FIG. 5) does not change much compared to FIG. 3, which is the response before LM is doubled. However, the load response (Fig. 6) is about 0.7 times the vibration frequency and the vibration attenuation is about 0.5 times that of Fig. 4, which is the response before LM is doubled. ing.

  As a method for solving the above problem, there is full closed loop control in which a load position, a load speed, or a load reaction force, which is a load state quantity, is measured and fed back. However, a sensor for measuring the load position, load speed, or load reaction force is installed between the load and the fixed coordinate system, and it is necessary to measure the relative state quantity between them. Therefore, it is not easy to install these sensors on the load. This is the reason why full-closed loop control for measuring and feeding back the load state quantity is not used in the majority of mechanical devices.

  An object of the present invention is to provide a position control method and apparatus that has a non-vibrating load response, a short settling time, and that is robust against load parameter variations.

  In order to achieve the above object, the present invention installs an acceleration sensor in a load. Unlike the position sensor and the speed sensor, the acceleration sensor measures the acceleration of the installed point with respect to the fixed absolute coordinate system. Therefore, the acceleration sensor can be installed at any point of the load as long as there is a space, and has the advantage that the acceleration at that point can be measured, which is not found in the position sensor and the speed sensor.

  Then, the proportional integral signal of the acceleration signal of the load obtained by the acceleration sensor is negatively fed back to the motor driving force command.

  Also, proportional or proportional integral control of the motor position is performed. Since the damping characteristic is obtained by feedback of the acceleration of the load, this control system does not become unstable. Also, there is no need for a motor speed feedback loop.

  As described above, according to the present invention, the acceleration of the load is fed back through the proportional integration element, and further, the position of the motor is controlled proportionally or proportionally. Therefore, the response of the load is non-vibrating, There is an effect that the settling time is increased, and further robust against fluctuations in the load mass.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  Referring to FIG. 7, there is shown a functional block diagram of a position control device according to an embodiment of the present invention. The purpose of the control is to make the load position respond according to the command. Performs proportional integral control of load acceleration and proportional or proportional integral control of motor position.

  In FIG. 7, the command unit 100 sends a driving force command for the motor 300 to the control unit 200, and the control unit 200 controls the motor 300 based on this command. The detection unit 500A (acceleration sensor provided in the load 400) monitors the acceleration of the load 400, and feeds this back to the control unit 200 to form a closed loop of acceleration. Further, the detection unit 500B (position sensor) monitors the position of the motor 300, and feeds this back to the control unit 200 to form a closed loop of the position.

  Referring to FIG. 8, a specific control block diagram of the position control device of the present embodiment is shown (used in the following simulation). Similarly to FIG. 2, the blocks (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) shaded in FIG. 8 are two inertial systems to be controlled.

  In FIG. 8, 1 is the reciprocal of the mass of the motor (MM is the mass of the motor), 2 is the integral characteristic from the motor acceleration to the motor speed (physical dynamic characteristic, s is the symbol of Laplace transform), 3 is the motor speed Integral characteristics to motor position (physical dynamic characteristics), 4 is the reciprocal of the load mass (LM is the load mass), 5 is the integral characteristic from load acceleration to load speed (physical dynamic characteristics), 6 is Integral characteristic (physical dynamic characteristic) from load speed to load position, 7 is an adder / subtractor, 8 is a stiffness between the motor and the load (Ks is a spring constant), and 9 is a damper (D Is a damping gain), and 10 is an adder.

  Here, the output of 3 is a motor position signal that is negatively fed back to the adder / subtractor 14. The motor position signal negatively fed back to the adder / subtractor 14 is passed to a position proportional controller 15 (Kpa is a position proportional gain) and a position integral controller 16 (Tia is a position integral time).

  On the other hand, the acceleration sensor 23 (Gacc is the gain of the sensor) obtains the load acceleration signal from the detected external force and the output of 4 (that is, the reciprocal of the mass of the load), and the acceleration proportional controller 24 (Kacc is the acceleration). Proportional gain) and acceleration integration controller 25 (Tacc is acceleration integration time). The acceleration signal that has passed through the acceleration proportional controller 24 and the acceleration integral controller 25 is input to the negative terminal of the adder / subtractor 17 via the adder 26 and is negatively fed back.

  These negative feedback signals, together with the driving force command output from the command generator 13, are a proportional device 18 (Km is a proportional gain) that compensates for the motor mass, and a delay element 19 (Ta) that approximates the dynamic characteristics of the current amplifier and the motor. Is passed through a time constant) and output to a two-inertia system. Reference numeral 11 denotes an adder / subtracter.

  Reference numerals 20 and 21 denote load disturbance force generators. In the following simulation, 20 generates a load disturbance force that rises in steps from zero to 100 N at t = 0.6. At 0.7, a load disturbance force falling from 100 N to zero is generated stepwise. Reference numeral 22 denotes a position recorder, which records the position of the motor, which is the output of 3, and the position of the load, which is the output of 6.

In FIG. 8, Kpa = 100 s ⁻¹ , Tia = 0.001 s, Km = 10 Ns / m, Ta = 0.005 s, MM = 10 kg, LM = 10 kg, Ks = (2π × 50) ² N / m, D = 0.1 × (2π × 50) Ns / m, Gacc = (1 / 9.8) s ² / m, Kacc = 250 s ⁻¹ , Tacc = 0.5 ms, position command, 1 mm at time t = 0 As a force disturbance, a response was simulated by adding a step disturbance from zero to 100 N at t = 0.6 and a step decrease from 100 N to zero at t = 0.7. .

  FIG. 9 is a response of the position of the motor by the position control device of the present embodiment. It can be seen that the motor is actively vibrating. FIG. 10 shows the response of the load position at this time. No vibration response is observed, the settling time is short, and the response to disturbance force is comparable to that of the position control device of the prior art. FIG. 11 shows the response of the motor position when the load mass LM is doubled. FIG. 12 shows the response of the load position at this time. In FIG. 12, the overshoot of the response of the load position with respect to the step position command is slightly increased. However, it is almost equal to the response shown in FIG. 10 and is robust to the variation of the load mass.

It is a functional block diagram of the position control apparatus of a prior art. It is a block diagram of the position control apparatus of a prior art. In the position control apparatus of a prior art, it is the figure which showed the response of the position of the motor with respect to a step position command and a pulse-like disturbance force. In the position control apparatus of a prior art, it is the figure which showed the response of the position of the load with respect to step position command and a pulse-form disturbance force. In the position control apparatus of a prior art, it is the figure which showed the response of the position of the motor with respect to a step position command and a pulse-like disturbance force when the mass of a load doubled. In the position control apparatus of a prior art, it is the figure which showed the response of the position of the load with respect to a step position command and a pulse-like disturbance force when the mass of a load doubled. It is a functional block diagram of the position control device of the present invention. It is a block diagram of the position control apparatus of this invention. In the position control apparatus of this invention, it is the figure which showed the response of the position of the motor with respect to a step position command and a pulse-like disturbance force. In the position control apparatus of this invention, it is the figure which showed the response of the position of the load with respect to a step position command and a pulse-like disturbance force. In the position control apparatus of this invention, it is the figure which showed the response of the position of the motor with respect to a step position command and a pulse-like disturbance force when the mass of a load doubled. In the position control apparatus of this invention, it is the figure which showed the response of the position of the load with respect to a step position command and a pulse-like disturbance force when the mass of a load doubled.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Command part 200 Control part 300 Motor 400 Load 500 Detection part 500A Detection part A (For load acceleration)
500B Detector B (for motor position)
1 Reciprocal of motor mass 2 Integral characteristic from motor acceleration to motor speed 3 Integral characteristic from motor speed to motor position 4 Reciprocal of load mass 5 Integral characteristic from load acceleration to load speed 6 Integral characteristic from load speed to load position 7 Adder / Subtractor 8 Stiffness between Motor and Load 9 Damper between Motor and Load 10 Adder 11 Adder / Subtractor 12 Adder 13 Command Generator 14 Adder / Subtractor 15 Position Proportional Controller 16 Position Integral Controller 17 Addition / Subtraction 18 Proportional device that compensates for motor mass 19 Delay element approximating dynamic characteristics of current amplifier and motor 20 Load disturbance force generator 21 Load disturbance force generator 22 Load and motor position recorder 23 Acceleration sensor 24 Proportional control of acceleration 25 Acceleration integral controller 26 Adder 27 Position proportional controller 28 Adder / subtractor 29 Speed proportional control 30 Speed of integral controller 31 adder 32 adder

Claims (2)

In a position control method for a load operated by a motor,
A signal indicating acceleration of the load is detected by an acceleration sensor provided in the load, and a proportional integral signal of the detection signal is negatively fed back to a driving force command for the motor,
A position control method comprising: negatively feeding back a proportional signal or proportional integral signal of the motor position signal to the driving force command. In a load position control device operated by a motor,
An acceleration sensor provided in the load;
Means for negatively feeding back a proportional integral signal of the signal indicating the acceleration of the load detected by the acceleration sensor to a driving force command for the motor;
A position control device comprising means for negatively feeding back a proportional signal or proportional integral signal of the motor position signal to the driving force command.

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