JP2819630B2 - Motor control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for smoothly controlling the speed of a motor even when the load changes.

2. Description of the Related Art In recent years, unmanned self-propelled vehicles have been increasingly used as unmanned and automated factories have advanced. Such a self-propelled vehicle is driven by a storage battery, runs at a constant speed, and requires smooth start / stop control. The motor control device is generally configured as shown in FIG. In FIG. 4, 1 is a motor, 2 is an encoder which generates a pulse in proportion to the rotation amount of the motor 1, 3 is a speed command means for giving a speed command of the motor 1, and 4 is a speed calculated from a pulse signal of the encoder 2. And the rotation speed of the motor 1
Speed control means for calculating a voltage applied to the motor 1 and outputting a PWM signal so that the rotation speed of the motor follows the speed command;
Is driving means for amplifying the PWM signal and supplying power to the motor 1.

The speed control means 4 may be composed of an analog circuit or a digital circuit. In the case of being constituted by a digital circuit, for example, there is a method as described in "System and Control", Vol. 26, No. 11, pp. 695-703, 1983. FIG. 3 shows a speed control block diagram of the speed control means 4 when it is constituted by a digital circuit.

FIG. 4 is a block diagram of a motor surrounded by a broken line in the block diagram of FIG. 3. Kt is the induced voltage constant of the motor,
Ke is the torque constant of the motor, J is the moment of inertia between the motor and the load, and R and L are the resistance and inductance of the windings of the motor. There are two methods of speed detection: a method that calculates the number of encoder pulses that come within a fixed sampling time, and a method that calculates the speed by counting the period of the encoder pulse with a reference clock and calculating the reciprocal thereof. ,
Either method is acceptable. The speed calculated as above is multiplied by Kf and compared with the command speed, the value obtained by multiplying the speed deviation by Kp and the value obtained by multiplying the speed deviation by Ki are added, and the change in the detected speed is further multiplied by Kd. Value is subtracted, and the result is Kv
Multiply and calculate the PWM output. Kf, Kp, Ki, Kd, and Kv are control constants. The PWM signal output value Vp is calculated by the following equation.

Vp = (Kp × E + Ki × I−Kd × d) × KV E: Difference between speed command and detected speed by speed deviation I: Value obtained by integrating speed deviation E by integral term D: Value obtained by detecting speed by acceleration Problems to be Solved by the Invention However, in the above-described method, when traveling with no load, such as a self-propelled vehicle, and when traveling with loaded or towed heavy objects, the situation is significantly different. ,
If the control constant is set according to the no-load condition, the delay with respect to the speed command will increase when a load is applied, and if the control constant is set according to the load, the There is a problem that it may be vibrated under a load.

SUMMARY OF THE INVENTION In view of the above problems, the present invention is to control the speed so that there is no delay or vibration of the speed under no load or under a load.

Means for Solving the Problems In order to solve the above problems, the present invention provides a motor, an encoder that generates a pulse in proportion to the rotation amount of the motor, speed command means for giving a motor speed command, and a pulse signal of the encoder. Speed control means for calculating the applied speed to the motor and calculating the applied voltage to the motor so that the motor speed follows the speed command and outputting a PWM signal, and amplifying the PWM signal to the motor so that the motor speed follows the speed command. A drive unit for supplying electric power, a unit for gradually increasing the voltage applied to the motor when the motor is started, and a unit for determining a control constant of the arithmetic control of the speed control unit from the applied voltage when the motor starts rotating are provided. When the motor starts, the applied voltage to the motor is gradually increased, and the control constant of the speed control of the speed control means is determined from the applied voltage when the motor starts to rotate, thereby controlling the motor speed. I control

Operation When a load is applied to the motor and the load torque increases, a large amount of current must be supplied to the motor, so that the voltage applied to the motor at startup varies depending on the size of the load.
The present invention gradually increases the applied voltage to the motor when the motor starts, estimates the magnitude of the load from the applied voltage when the motor starts to rotate, and experimentally obtains the magnitude in advance according to the magnitude of the load. The motor speed is controlled by using the control constant of the arithmetic control of the speed control means obtained or calculated by calculation. Therefore, since the optimal control constant is determined according to the load at the time of starting the motor, the speed control can be performed such that the speed is not delayed or the vibration does not occur even when there is no load or when the load is applied.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a motor control device according to the present invention, and FIG. 2 is a flowchart of speed control. First, FIG. 1 will be described. In FIG. 1, 1 is a motor, and 2 is an encoder that generates a pulse in proportion to the rotation amount of the motor. Reference numeral 3 denotes speed command means for giving a speed command of the motor, 31 is a CPU for calculating speed command data, 32 is a ROM storing a processing program of the CPU 31, and 33 is temporarily used when the CPU 31 executes arithmetic processing. The RAM 34 is an I / O for inputting a signal from a sensor or the like or outputting a signal to the outside.
Reference numeral 4 denotes speed control means for calculating a speed from a pulse signal of the encoder, setting the rotation speed of the motor as a rotation speed of the motor, calculating an applied voltage to the motor 1 so that the rotation speed of the motor follows the speed command, and outputting a PWM signal. 41 is a CPU that performs arithmetic processing of speed control, and 42 is an RO that stores a processing program of the CPU 41.
M and 43 are used temporarily by the CPU 41 when executing arithmetic processing or CP
A two-port RAM 44 for transferring data to and from U31 is a counter for counting pulses from the encoder 2. 5 is a driving means for amplifying the PWM signal and supplying power to the motor, 51 is a DC power supply for driving the motor 1, 52 is a resistor for detecting a current flowing from the DC power supply, and 53 is a resistor 52. A current limiting circuit for limiting the detected current; 54, 55, 56, and 57 are power MOSFETs for flowing current to the motor 1; and 58 is a pulse width proportional to the pulse width data of the PWM signal calculated by the CPU 41. PWM signal circuits for converting the signals into signals and amplifying them and sending gate signals to the power MOSFETs 54, 55, 56 and 57, and 60, 61, 62 and 63 are freewheel diodes.

Next, the operation will be described. In FIG. 1, it is assumed that the motor 1 is now stopped. When a sensor signal for rotating the motor 1 at a certain speed is input from the outside to the I / O 34, the CPU 31 reads and executes the pre-programmed processing contents from the ROM 32 and writes the speed command data into the 2-port RAM 43. The CPU 41 executes the program stored in the ROM 42 and having the contents shown in the flowchart of FIG.

Next, the operation will be described with reference to the flowchart of FIG. CP
When U41 reads the speed command data from the CPU 31 from the 2-port RAM 43, the U41 converts the pulse width data of the PWM signal of a certain value into PWM.
The PWM circuit 58 converts the signal into a pulse width signal proportional to the pulse width data, amplifies the signal, and amplifies it.
5, or a gate signal is sent to the power MOSFETs 56 and 57, and a voltage is applied to the motor 1. The CPU 41 reads the data of the counter 44 and checks whether the value of the counter 44 has changed. If the value of the counter 44 has changed, it means that the speed has changed. If the value of the counter 44 has not changed, since the speed has not changed, the pulse width data of the PWM signal is increased by a predetermined value from the previous time and sent to the PWM circuit 58. The PWM circuit 58 converts the signal into a pulse width signal proportional to the pulse width data, amplifies the signal,
A gate signal is sent to the ETs 54 and 55 or the power MOSFETs 56 and 57 to apply a voltage to the motor 1. The CPU 41 reads the value of the counter 44 as in the previous case and checks whether the speed has changed. If the speed has not changed, the same processing is repeated to increase the voltage applied to the motor 1. When the speed changes, it is determined that the motor 1 has started to rotate, and the PWM at that time is determined.
The control constants Kf, Kp, Ki, Kd, and kv are set from the pulse width data of the signal as shown in the block diagram of the speed control in FIG. 3, and the data is read from the counter 44 to calculate the speed. Calculates the voltage applied to the motor 1 and outputs the pulse width data of the PWM signal to the PWM output circuit 58, as shown in the block diagram of the speed control, and repeats the calculation to perform the speed control. Do it. The control constants Kf, Kp, Ki, Kd, and kv determined from the pulse width data of the PWM signal are obtained in advance experimentally according to the magnitude of the load, or values obtained by calculation are stored in the ROM 42 as a table. ing.

As described above, according to the present embodiment, the applied voltage to the motor is gradually increased at the time of starting the motor, the magnitude of the load is estimated from the applied voltage when the motor starts rotating, and the optimal control constant is determined. Therefore, the control speed can be controlled so that there is no speed delay or vibration even when there is no load or when a load is applied.

In the present embodiment, the DC motor is driven, but it goes without saying that the same applies to the AC motor. Although the control block diagram of the speed control means does not include a current control loop which is a minor speed loop, there is no problem even if a current is detected and a current control loop is inserted.

Effects of the Invention As described above, according to the present invention, the applied voltage to the motor is gradually increased at the time of starting the motor, the magnitude of the load is estimated from the applied voltage when the motor starts to rotate, and the optimal control constant is determined. Since it is determined, there is an effect that the speed can be controlled so that there is no delay or vibration of the speed even when there is no load or the load is applied.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention, FIG. 2 is a flowchart of the speed control, and FIG. 3 is a speed control block diagram of a speed control means in the case of a digital circuit. FIG. 4 is a block diagram of a general motor control device. 1 ... motor, 2 ... encoder, 3 ... speed command means, 4 ... speed control means, 5 ... drive means.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-198604 (JP, A) JP-A-56-121389 (JP, A) JP-A-58-192487 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) H02P 5/00-5/405 H02P 7/00-7/34

Claims (1)

(57) [Claims] 1. A motor, an encoder for generating a pulse in proportion to the amount of rotation of the motor, speed command means for giving a speed command for the motor, and a motor for rotating the motor by calculating a speed from a pulse signal of the encoder. Speed control means for calculating a voltage applied to the motor and outputting a PWM signal so that the rotation speed of the motor follows the speed command as a speed, and amplifying the PWM signal to supply power to the motor Drive means, means for gradually increasing the voltage applied to the motor when the motor is started, and means for determining a control constant for arithmetic control of the speed control means from the applied voltage when the motor starts rotating. Motor control device.