JP3747767B2 - Speed detection method for motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a speed detection method for a motor control device.
[0002]
[Prior art]
In recent years, with the advancement of CPUs and peripheral ICs, digitization of control has become common, and control that is difficult to achieve with analog control greatly contributes to high performance and high functionality of equipment.
[0003]
This will be described with reference to a speed control block diagram of a general motor control device.
[0004]
In FIG. 4 , the motor control device 3 obtains the motor position 4 from the encoder 2 attached to the motor 1. The motor position 4 is sampled by the sampler 5 at the start of the speed control cycle and used for the current speed control calculation.
[0005]
The sampled motor position 6 is converted to a motor speed 8 by a conventional speed detector 15. From the given speed command 9 and the detected motor speed 8, the speed controller 10 calculates a torque command 11 and gives the command to the current controller 12. The current controller 12 controls the motor current 13 so that the motor generates a torque equal to the torque command 11.
[0006]
Here, FIG. 3 shows a flowchart of the processing in the conventional speed detector 15. Here, there is only step S51 for calculating the motor speed at the start of sampling this time.
[0007]
FIG. 5 shows a timing chart of the processing in the motor control device 3.
[0008]
The encoder pulse 16 is converted into a count value 17 in the motor control device 3, and is sampled and held at every speed control period 18 to become a discretized value.
[0009]
Based on this value, the speed control process 19 is performed. In general, the speed control processing 19 is often digitally calculated by a microcomputer or the like, but this inevitably generates a speed calculation delay Td1.
[0010]
Further, when the current control process 21 is digitally calculated, the torque command calculated in the speed control process 19 is given to the current control process 21 every current control period 20, so that a transfer delay Td2 occurs. Further, there is a current delay Td3 due to a calculation delay of the current control process 21 itself and a response delay until the motor current actually changes. Eventually, there will be a delay of Td1 + Td2 + Td3 from when the position information is sampled until the motor current changes.
[0011]
[Problems to be solved by the invention]
Since this delay becomes a phase delay element of the speed closed loop control system, it has been a major obstacle to improving the speed response.
[0012]
Conventionally, Td1, Td2 and Td3 have been reduced by shortening the time of the speed control cycle and the current control cycle, but this requires the use of a high-performance CPU and is limited by problems such as cost.
[0013]
Further, as long as digital control is performed, this delay does not become zero, so that there is a problem in terms of responsiveness with respect to the speed control system by analog control.
[0014]
An object of the present invention is to solve this conventional problem and to provide means for compensating for a phase delay of a speed closed loop and improving the response of a speed control system.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention uses a speed estimation value and disturbance torque information calculated using a speed observer, estimates future speed information for a set time, and uses it for control. It is possible to accurately compensate for the phase delay of the control and improve the response.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve the above-described problems, the present invention compares a speed detection circuit that calculates a motor speed from encoder information obtained by detecting a motor position at each control cycle, and compares the speed detection value with a given speed command value to obtain a torque command. In a motor controller equipped with a speed controller to be generated and a current controller that controls the motor current according to the torque command, a disturbance observer is used to calculate the motor speed at the start of the control cycle , and the estimated disturbance torque obtained from the speed observer Is added to the previously calculated torque command value, and the value divided by the total inertia of the motor and load is the time until the motor current actually changes according to the torque command calculated from the start of the control cycle. And the result obtained by adding the speed detection value at the start of the current control cycle to the value is used as a speed detection value for control.
[0017]
As a result, the phase delay of the speed closed loop system due to Td1, Td2, and Td3 is accurately corrected, and the best future speed can be estimated, so that the best response performance can be obtained.
[0018]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
(Example 1)
FIG. 1 is a block diagram of the speed control system of the first embodiment, and is the same as FIG. 4 except that the torque command 11 is input to the speed detector 14.
[0020]
The processing in the speed detector 14 will be described with reference to a flowchart showing the processing.
[0021]
In FIG. 2 , the speed observer generally corrects the estimated value based on the error between the motor position estimated value based on the load model shown in step S41 and the motor position estimated value shown in step S42 and the actual motor position. Consists of As a result, the motor speed at the start of sampling is accurately estimated, and at the same time, an estimated value of disturbance torque is obtained.
[0022]
If the load inertia is J, it is possible to estimate the future speed in consideration of the disturbance torque with the calculation formula of step S43 in which the motion equation of the rotating system is discretized, and further set the delay time of Td1 + Td2 + Td3 in FIG. By doing so, it is possible to perform speed control that accurately compensates for the phase delay from speed detection to torque output.
[0023]
【The invention's effect】
As is clear from the above-described embodiment, according to the present invention , it is possible to accurately estimate the future speed by optimally adjusting the speed observer, so that the delay time until the torque command is actually reflected By accurately estimating the future motor speed only and using it for the subsequent speed control, accurate phase delay compensation of the speed control becomes possible. Thereby, the phase delay of the speed closed loop can be compensated in a wide range, and the effect of improving the responsiveness of the speed control system can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of motor speed control processing in Embodiment 1. FIG . 2 is a flowchart of motor speed detection processing in Embodiment 1. FIG. 3 is a flowchart of speed detection processing in conventional motor control. Block diagram [Figure 5] Conventional motor control processing timing chart [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor 2 Encoder 3 Motor control apparatus 4 Motor position 7, 14 Speed detector 8 Motor speed 9 Speed command 10 Speed controller 11 Torque command 12 Current controller 13 Motor current 18 Speed control cycle 19 Speed control processing 20 Current control cycle 21 Current control processing

Claims (1)

A speed detection circuit that calculates the motor speed from encoder information that detects the motor position for each control cycle, a speed controller that generates a torque command by comparing the speed detection value with a given speed command value, and a motor current according to the torque command In a motor control device equipped with a current controller for controlling the motor, a speed observer is used to calculate the motor speed at the start of the control cycle , and the estimated disturbance torque obtained by the speed observer is added to the previously calculated torque command value. The value obtained by dividing the value by the total inertia of the motor and load is multiplied by the time until the motor current actually changes according to the torque command calculated from the start of the control cycle. A speed detection method for a motor control device, wherein the result obtained by adding the detected speed values is used as a detected speed value for control.