JPH01314312A - Servo controller - Google Patents

Abstract

PURPOSE:To prevent deterioration in controllability due to the temperature rise of an element incorporated in an output amplification part by outputting a control signal from a control part in response to either of a position and a speed signal. CONSTITUTION:A temperature detection part 8 is added to detect the temperature of the current amplifying element incorporated in the power amplification part 3 and sends its temperature signal out to a microcomputer control part 1. The microcomputer control part 1 estimates the internal resistance of the current amplifying element as a function of temperature from the temperature signal from the temperature detection part 8. The control signal (a) from the control part 1 is so outputted as to maintain the specific duty ratio of, for example, the driving current A from the output amplification part 3. Consequently, the deterioration in the controllability of the device, i.e. deterioration in response and stability is prevented and excellent control is maintained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention particularly relates to a servo control device that prevents deterioration in controllability due to temperature rise of elements built in an output amplification section.

[Conventional technology]

A conventional example will be explained with reference to FIG. This conventional example is a digital servo control device using a microcomputer to control the position of a DC servo motor, and FIG. 2 is a block diagram showing its configuration. In FIG. 2, when driving the DC servo motor 4 (hereinafter simply referred to as the motor), the microcomputer control unit 1 sets the rotation angle target value of the motor 4 based on an arbitrary control law at every fixed control period. , a current command a for driving the motor 4 and a motor drive torque direction from the current rotation angle value of the motor 4 obtained through a pulse encoder 5 directly connected to the motor 4, a motor forward/reverse discrimination section 6, and a counter 7. Calculates the command and outputs it. A PWM (pulse width modulation) control section 2 converts the current command a into a current control command C for PWM controlling the current amplification element in the power amplification section 3, and outputs the current control command C. The power amplification unit 3 outputs the motor drive current A by controlling the current control command C@PWM as a DC voltage. The motor 4 is driven by a motor drive current A with a predetermined torque.

[Problem to be solved by the invention]

As described above, in the conventional technology, the power amplification section 3 is configured as an H-type bridge circuit, and when a current flows through the current amplification element, the current amplification element generates heat due to its internal resistance, and its temperature rises. Furthermore, since this internal resistance has a positive temperature coefficient, it increases as the temperature of the current amplifying element increases. Therefore, as the temperature of the current amplification element increases, the motor drive current A, which is the output of the power amplification section 3 in response to the current control command C, decreases, and the torque generated by the motor 4 also decreases. In this way, the conventional servo control device does not take into account the temperature rise of the current amplification element built into the power amplification section 3, and therefore, for example, if the operation continues with frequent repeated acceleration and deceleration operations, There was a drawback that the drive torque of the motor 4 with respect to the current command a decreased, resulting in poor controllability of the motor. An object of the present invention is to provide a servo control device that solves the problems of the conventional technology and prevents deterioration in controllability due to temperature rise of elements built into an output amplification section. be.

[Means to solve the problem]

In order to solve this problem, a servo control device according to the present invention includes: a servo motor; a control section that outputs a control signal based on at least one of a position signal and a speed signal from the servo motor; an output amplification section that outputs a drive signal for the servo motor based on a signal, the device comprising: a temperature detection section that detects the temperature of the output amplification section and sends this temperature signal to the control section; The control section outputs the control signal based on the temperature signal as well as at least one of the position signal and speed signal.

[For use]

The temperature detection section detects the temperature of the output amplification section, and this temperature signal is input to the control section. The control signal from the control section is output based on at least one of the position signal and the speed signal as well as the temperature signal so that, for example, the drive current from the output amplification section maintains a predetermined duty ratio.

【Example】

An embodiment of a servo control device according to the present invention will be described with reference to FIG. This embodiment is a digital servo control device using a microcomputer to control the position of a DC servo motor, and FIG. 1 is a block diagram showing its configuration. In FIG. 1, this embodiment differs from the conventional example described with reference to FIG. 2 in that a temperature detection section 8 is added. Note that units having the same functions are given the same reference numerals as in FIG. 2. The temperature detection section 8 is a thermistor, for example, and detects the temperature of the power amplification section 3, more precisely, the temperature of the built-in current amplification element, and sends the temperature signal to the microcomputer control section 1. The operation of this embodiment is as follows. In FIG. 1, a microcomputer control unit 1 generates a current command a for driving a motor 4 and a motor drive torque direction based on an arbitrary control law every fixed control period, as in the conventional device described above. Calculate and output the command. At the same time, the microcomputer control section 1 estimates the internal resistance of the current amplification element as a function of temperature from the temperature signal from the temperature detection section 8, and corrects the current command a based on this estimation. A method for correcting this current command a will be specifically explained. Now, it is assumed that the internal resistance of the current amplification element is expressed as a linear function of temperature as shown in equation (1) below. In this case, considering the characteristics of the current amplifying element, the temperature was set at 25°C. That is, when temperature correction of the current command a is not performed, the value at a temperature of 25° C. (reference temperature) is applied to the internal resistance of the current amplifying element. Rt = K-T + Rs...
・-(1) Here, Rt: Temperature T″C of the current amplification element
Internal resistance at R3: same reference temperature (25°C)
internal resistance, K: proportional constant; when T<25°C, K=O1 when T≧25°C, K=Kc (positive constant). Next, when determining the motor drive current A for the current command a for the reference temperature and the temperature T″C, the reference temperature is:
As = VDs / (Rm +Rs) - (2) Temperature T″C: At =VDt / (Rm +Rt)
-(3) Here, As, At: reference temperature, temperature T''
Drive current at C, ■=DC voltage, Ds, Dt: reference temperature. Duty ratio (current command value/maximum value of current command) at temperature T'C, RIIl: resistance of motor armature. In equations (2) and (3), generally Rt > Rs, so if Ds = Dt, At < As. Therefore, in order to keep the driving torque of the motor 4 constant regardless of the temperature, it is necessary to correct the current command a so that At = As. Therefore, VDs / (Rm + Rs) = VDt
/(Rm+Rt) and K-T is Rm, Rs, Rt
Since it is extremely small compared to , the following equation holds approximately. Dt = (1+ to -T/ (Rm +Rs)) Ds
=(1+Ft)Ds ・・・・・・(
4) However, Ft = −T/ (Rm +Rs) Therefore, the duty ratio Dt at temperature T″C is (4)
By correcting the current command a so as to satisfy the equation, it is possible to prevent the drive torque of the motor 4 from decreasing due to the temperature rise of the current amplifying element. As a result, the controllability of the motor 4 is maintained well without deterioration.

【Effect of the invention】

As explained above, in the present invention, the temperature detection section detects the temperature of the output amplification section, and this temperature signal is input to the control section. The temperature signal from this control section is
Based on the temperature signal as well as at least one of the position signal and the speed signal, for example, a drive current from the output amplification section is outputted so as to maintain a predetermined duty ratio. Therefore, the present invention has the following superior effects compared to the conventional technology. (1) Deterioration of controllability of the device, that is, deterioration of coordination and stability, is prevented, and good control is maintained. (2) At the same time, it is confirmed that the output amplification section or its built-in elements are used at a temperature below the permissible temperature, which improves the reliability of the device. (3) Since the additional parts in the structure of the device are simple, it is easy to implement and the cost increase is small.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention; FIG. 2 is a block diagram showing the configuration of a conventional example. Symbol explanation 1: Microcomputer control section, 2: PWM control section, 3: Power amplification section, 4: DC servo motor, 8: Temperature detection section.

Claims (1)

[Claims] 1) A servo motor, a control unit that outputs a control signal based on at least one of a position signal and a speed signal from the servo motor, and an output amplification that outputs a drive signal for the servo motor based on the control signal. The device includes a temperature detection section that detects the temperature of the output amplification section and sends the temperature signal to the control section, and the control section is configured to detect the temperature of the output amplification section and send the temperature signal to the control section, and the control section may detect the temperature of the output amplification section and send the temperature signal to the control section. . A servo control device, characterized in that the control signal is output based on the temperature signal.