JP5074816B2 - Motor drive system and motor drive method - Google Patents

Description

  The present invention relates to a motor drive system and a motor drive method for driving a motor with a PWM signal, and more particularly to a motor drive system and a motor drive method for performing feedback control of a PWM signal based on a position detection result of the motor.

  In electric motor control devices used in various fields, a position detector (encoder) is provided to detect the rotation angle of the electric motor. The position detection signal from this position detector is supplied to the control means of the motor driver circuit of the electric motor, and generates a PWM waveform to be supplied to the motor driver circuit based on the position information of the electric motor indicated by the position detection signal.

Here, when the wiring of the position detector is reduced by serial transmission, a signal wiring is required separately from the motor drive line. In order to eliminate such separately required wiring, Patent Document 1 discloses a motor that is reduced in size by supplying a motor driving current and a control signal through a common wiring system, thereby reducing harnesses and connectors. A control system is disclosed.
In this conventional motor control system, a direct current serving as a driving power source for a motor and a control signal generated by the controller are input and superimposed on a mixer of the controller. From the mixer, the high-frequency control signal superimposed on the direct current is conveyed to the motor duplexer via the power line carrier communication cable. The duplexer separates the direct current and the control signal, the direct current serves as a driving power source for the motor, and the control signal is input to the control unit to perform various controls of the motor. In this way, power line carrier communication in which a control signal is superimposed on a direct current is performed. Therefore, a set of power line carrier communication connectors and a set of power line carrier communication cables may be provided on the controller side and the motor side, respectively.
JP 2003-319893 A Japanese Patent Laid-Open No. 2001-231284 JP 2006-94623 A

  However, if a signal is superimposed on a motor drive line as in Patent Document 1, the influence of noise from the drive line is large, and the signal must be superimposed on a DC power supply. There is also a problem that the circuit scale for signal superposition and separation becomes large.

  On the other hand, there is a method of reducing the influence of switching noise by shifting the detection timing of current and voltage that can be detected in a relatively short time with respect to the switching timing (see, for example, Patent Documents 2 and 3). If the timing of the signal changes sequentially and a long time is required for signal detection (communication), for example, serial communication time required for position acquisition is required, reliable signal detection (communication) cannot be performed. is there.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a motor drive system and a motor drive method capable of reliably performing position detection even when switching noise occurs. To do.

  The motor drive system according to the present invention includes an electric motor, drive means for driving the electric motor by a switching operation, position detection means for detecting the position of the electric motor, and the drive based on the detection result of the position detection means. Control means for controlling the means, wherein the control means temporarily stops the switching operation of the drive means and controls the drive means based on at least the position detection signal received during the stop period.

  In the present invention, since the switching operation is temporarily stopped and the position detection signal is received during that time, the influence of the switching noise on the position detection signal can be reduced.

  The control means is connected to the electric motor via a transmission line, generates a plurality of drive voltages for driving the electric motor, and a position detection signal from the position detection means. It is preferable to include feedback means for feedback-controlling the drive voltage generation means and stop means for temporarily stopping switching of the drive voltage in the drive voltage generation means. The switching operation can be stopped by temporarily stopping the switching of the drive voltage.

  Furthermore, the position detection signal can be transmitted using a transmission path through which a driving voltage is sent, and thus wiring can be saved.

  Furthermore, the stop means can stop the switching of the drive voltage for two or more cycles of transmitting the position information based on the position detection signal, thereby reliably detecting the position detection signal. Can be received.

  In addition, the stopping unit can periodically stop the switching of the driving voltage, or can stop the switching of the driving voltage in response to a request from the feedback unit. Appropriate stop timing can be achieved according to switching noise in the transmission line.

  Further, the stop means can notify the feedback means of the timing for stopping the switching of the drive voltage, whereby the feedback means can recognize the timing when the switching noise is reliably reduced.

  Furthermore, the position detection signal can have a specific start bit pattern indicating the start of position information, and the communication time of the position detection signal can be shortened by providing the start bit pattern.

  Further, the position detection means may output the position detection signal while the switching operation is stopped by the stop means.

  Furthermore, the electric motor can be provided at a joint portion of the robot apparatus. For example, the electric motor can be provided at a joint section of a robot apparatus such as an autonomous walking robot apparatus that is highly demanded for weight reduction and downsizing.

  The motor driving method according to the present invention includes at least a step of stopping the switching operation at a predetermined timing while driving the electric motor by the switching operation of the driving means, and a position detection signal for detecting the position of the electric motor. And a step of feedback-controlling drive voltage generation means for generating a plurality of drive voltages for driving the electric motor based on the position detection signal acquired during the period.

  According to the present invention, it is possible to provide a motor drive system and a motor drive method capable of reliably performing position detection even when switching noise occurs.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a motor drive system according to the present embodiment. The motor drive system 100 according to the present example is suitable for driving an electric motor provided at a joint portion of a robot apparatus such as an autonomous walking robot apparatus that is highly demanded for weight reduction and miniaturization. And the motor drive system 100 concerning this Embodiment reduces the influence which switching noise has on signal transmissions, such as a position detection signal, with a simple circuit.

  As shown in FIG. 1, a motor drive system 100 includes a motor driver circuit 2, a transmission path 6, a switching noise suppression core 3, and capacitors 4a, 4b, 7a, and 7b for separating a position detection signal from the transmission path in a DC manner. The differential signal transmitter 8, the differential signal receiver 5, the electric motor 9, the position detector 10, and the control unit 1 that controls the driving of the electric motor 9 based on the detection results of the position detector 10 are provided. Among these, the control part 1 and the motor driver circuit 2 are provided in the trunk | drum part of a robot apparatus, and the electric motor 9 and the position detector 10 are provided in each joint part.

  The motor driver circuit 2 is a driving means for driving the electric motor 9 by a switching operation. The motor driver circuit 2 receives a PWM signal from a PWM generation circuit 11 to be described later, and drives each of U-phase, V-phase, and W-phase drive voltages according to the PWM signal. Is generated and output. Specifically, the motor driver circuit 2 includes a plurality of transistors and diodes.

  The transmission path 6 is a three-phase power line composed of three motor cables that transmit the U-phase, V-phase, and W-phase drive voltages output from the motor driver circuit 2 to the electric motor 9.

  The switching noise suppression core 3 is a core made of ferrite, amorphous magnetic material, or the like for suppressing noise generated by transistor switching in the motor driver circuit 2.

  The electric motor 9 is a permanent magnet motor (servo motor) that inputs U-phase, V-phase, and W-phase drive voltages and rotates a rotating shaft in accordance with each drive voltage signal. That is, the electric motor 9 according to this example is a three-phase motor.

  The position detector 10 is a rotary encoder that detects the rotation angle of the rotation shaft of the electric motor 9. A position detection signal from the position detector 10 is input to the differential signal receiver 5 from the capacitors 4a and 4b via the transmission path 6 from the differential signal transmitter 8 and the capacitors 7a and 7b. Is input.

  The control unit 1 includes a PWM generation circuit 11, a feedback circuit 12, a switching stop circuit 13, and a transmitter 14, and temporarily stops the switching operation of the motor driver circuit 2 and receives a position detection signal received at least during the stop period. The motor driver circuit 2 is controlled on the basis of, for example, a controller.

  The PWM generation circuit 11 is a drive voltage generation unit that is connected to the electric motor 9 via the transmission path 6 and generates a plurality of drive voltages for driving the electric motor 9, and feeds back a signal from the transmitter 14 as feedback. The PWM signal has a pulse width corresponding to the drive current command signal input from the circuit 12. The PWM generation circuit 11 according to the present embodiment generates and outputs each of the U phase, the V phase, and the W phase.

  The feedback circuit 12 is feedback means for feedback-controlling the PWM generation circuit 11 based on the position detection signal from the position detector 10, and includes a position detection signal transmitted from the position detector 10 and a target value given from the host device. And the PWM generation circuit 11 is feedback-controlled so that they match.

  The switching stop circuit 13 is a stop means for temporarily stopping the output of the drive current command signal in the PWM generation circuit 11, and in the present embodiment, the cycle in which the position detector 10 transmits the position information by the position detection signal. The drive current command signal of the PWM generation circuit 11 is stopped for two cycles or more. Although it becomes difficult to detect the position detection signal due to switching noise at the time of PWM waveform generation, the position detection signal is sent to the feedback circuit 12 by stopping the generation of the PWM waveform in a range where there is not much influence on the output of the electric motor 9. Can be reliably received.

  In the present embodiment, by temporarily stopping the output of the PWM waveform by the switching stop circuit 13, it is possible to easily superimpose a motor position detection signal or the like on the motor drive line. Next, the switching stop of the switching stop circuit 13 will be described. FIG. 2 is a diagram illustrating a PWM waveform, switching noise, and a position detection signal.

  When a position detection signal is transmitted from the position detector 10 attached to the electric motor to the control unit 1, the position detection signal is affected by switching noise generated by driving the motor. For this reason, in order to ensure communication quality, it is necessary to take noise countermeasures using differential transmission, noise removal filters, error correction, shielded cables, and the like. When the position detection signal is superimposed on the transmission path 6 that is a motor power line as in the present embodiment, it is further difficult to take measures.

  By the way, the normal switching noise frequency is about several kHz to 20 kHz (period 50 μs), and switching can be ensured only in one period, for example, about 3.2 μs. That is, for example, when switching noise is generated 12 times in total for the three phases, upper and lower arms, PWM rise and fall, and the noise time generated by one switching is 1 μs, there is no noise in one cycle. Is 3.2 μs at (50 μs-1 μs × 12 times) / 12 times.

  On the other hand, for example, if it is not necessary to increase the control gain, the interval of transmission of position information by the position detection signal is sufficient at intervals of 500 μs (2 kHz). That is, it is only necessary that the position information can be transmitted at a frequency of once every 10 switching operations. Further, the time required for communication is, for example, about 4 μs when 32-bit information is transmitted at a communication speed of 10 Mbps.

  Therefore, noise that affects communication is predominantly noise generated at the time of switching. Therefore, switching is performed at a frequency of, for example, once every 10 cycles, and is twice or more the time required for transmission of position information (period T ) Stop and communicate location information during that time. As a result, the influence of noise due to switching can be reduced. Stopping switching has a trade-off relationship with motor response and maximum torque, but motor characteristics are also important in places where a large number of motors are used, such as robot hands. It is essential, and wiring saving is extremely important.

  Here, if the transmission of the position detection signal from the position detector or the like is always performed regardless of the stop of the switching, the control unit 1 can acquire the position information when the position can be acquired. There is no need.

  In the present embodiment, the switching operation of the motor driver circuit 2 is stopped for a predetermined period or a predetermined time for each predetermined period, that is, twice the time necessary for transmitting position information. Since switching noise does not occur during this stop period, information can be exchanged between the position detector 10 and the control unit 1 without much noise countermeasures. Conventionally, when a position detection signal is superimposed on a motor drive line, it has been necessary to provide a filter or the like to prevent switching noise, and there has been a problem that the circuit scale of the control unit is increased. By applying the system, the position detection signal can be easily superimposed on the motor drive signal.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the position detection signal can detect the beginning of the position detection information as a blank period (0) in which no signal is transmitted, for example, the first 16 bits, but by providing a start bit pattern The blank period can be eliminated and synchronization can be achieved in a short time. Thereby, the frequency | count of information transmission per unit time can be increased as much as possible, and the feedback control with respect to the control part 1 can be made more accurate. Alternatively, it is possible to suppress a reduction in motor characteristics of the electric motor 9 by shortening the transmission time of the position detection signal.

  In the above-described embodiment, the switching operation is periodically stopped. However, the switching can be stopped only when the position information cannot be recognized. In this case, for example, the switching stop circuit 13 receives the error notification from the feedback circuit 12 that recognizes the position detection signal, and stops the switching operation only when the error notification is received. As a result, it is possible to suppress a decrease in motor characteristics while acquiring position information.

It is a block diagram showing a motor drive system concerning an embodiment of the invention. It is a figure which shows a PWM waveform, switching noise, and a position detection signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control part 2 Motor driver circuit 3 Switching noise suppression core 4a, 4b, 7a, 7b Capacitor 5 Differential signal receiver 6 Transmission path 8 Differential signal transmitter 9 Electric motor 10 Position detector 11 PWM generation circuit 12 Feedback circuit 13 Switching stop circuit 14 Transmitter 100 Motor drive system

Claims (11)

An electric motor;
Driving means for driving the electric motor by a switching operation;
Position detecting means for detecting the position of the electric motor;
Control means for controlling the drive means based on the detection result of the position detection means,
The position detection means always transmits a position detection signal to the control means regardless of the stop of the switching operation of the drive means,
The control means is a motor drive system for temporarily stopping the switching operation of the drive means and controlling the drive means based on the position detection signal received at least during the stop period. The control means includes
Drive voltage generating means connected to the electric motor via a transmission line and generating a plurality of drive voltages for driving the electric motor;
Feedback means for feedback controlling the drive voltage generation means based on a position detection signal from the position detection means;
The motor drive system according to claim 1, further comprising: a stop unit that temporarily stops switching of the drive voltage in the drive voltage generation unit. 3. The motor drive system according to claim 2, wherein the stop unit stops switching of the drive voltage for at least two cycles of a cycle of transmitting position information based on the position detection signal. It said stop means is a motor drive system according to claim 2 or 3, characterized in that stops the switching of the regular driving voltage. It said stop means is a motor drive system according to any one of claims 2 to 4, characterized in that stopping the switching of the drive voltage in response to a request of the feedback means. The motor drive system according to any one of claims 2 to 5 , wherein the stop unit notifies the feedback unit of a timing at which the stop unit stops the drive voltage. The motor drive system according to any one of claims 2 to 6 , wherein the position detection unit outputs the position detection signal while the switching of the drive voltage is stopped by the stop unit. The motor drive system according to any one of claims 1 to 7, wherein the position detection signal has a specific start bit pattern indicating the start of position information. The motor drive system according to any one of claims 1 to 8, wherein the position detection signal is transmitted using a transmission path through which a drive voltage is sent. The motor drive system according to any one of claims 1 to 9, wherein the electric motor is provided in a joint portion of a robot apparatus. A step of stopping the switching operation at a predetermined timing while driving the electric motor by the switching operation of the driving means;
Always sending a position detection signal for detecting the position of the electric motor to the control means regardless of the stop of the switching operation;
And a feedback control of a drive voltage generation means for acquiring a plurality of drive voltages for driving the electric motor based on the position detection signal and acquiring the position detection signal at least during the stop period.

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