KR100858020B1 - Apparatus and method for controlling position of a motor using pulse width modulation - Google Patents

Abstract

The present invention relates to an apparatus and method for controlling a motor using pulse width modulation (PWM).

Motor control apparatus according to an embodiment of the present invention, the motor generating a predetermined motion, the position sensor for detecting a sensor value of the current position of the motor, the sensor value and the target value to be compared by comparing the error value A control decision loop for obtaining a signal, a pulse controller for adjusting the pulse width and the number of pulses of the PWM signal according to the obtained error value, and a motor driver for driving the motor by the power input to the motor based on the adjusted PWM signal. .

PWM, motor, pulse width, number of pulses, branch signal

Description

Apparatus and method for controlling position of a motor using pulse width modulation}

1 is a view showing a motor driving method by pulse width control according to a first embodiment of the present invention.

2 shows the generation of two signal pairs input to a motor driver.

3 is a diagram illustrating a motor driving method using pulse number control according to a second exemplary embodiment of the present invention.

4 shows the relationship between the duty cycle and the control of the motor.

5 is a view showing a motor driving method by controlling the pulse width and the number of pulses according to the third embodiment of the present invention.

6 is a view showing a motor driving method by a branch signal according to a fourth embodiment of the present invention.

7 shows an example of changing a pulse width by a branch signal;

8 illustrates a relationship between a duty cycle and control of a motor according to another embodiment of the present invention.

9 is a diagram showing a configuration of a motor control apparatus according to an embodiment of the present invention.

10 is a flowchart showing a motor control method according to an embodiment of the present invention.

(Symbol description of main part of drawing)

100: motor control unit 110: A / D converter

120: signal processor 130: control decision loop

140: oscillator 150: pulse control unit

151 pulse width adjusting unit 152 pulse number adjusting unit

153: branch signal application unit 160: power

170: motor driver 180: motor

190: position sensor

The present invention relates to an apparatus and method for controlling a motor using pulse width modulation (PWM).

Analog signals with unrestricted resolution in both time and magnitude have continuously varying values. Batteries listed with a specific voltage value may have an arbitrary real value, with the output voltage always changing over time rather than the exact voltage value. Likewise, the amount of current output from the battery is not limited to a constant value. In contrast, digital signals are distinguished from analog signals in that they always have values within a limited set, such as a predetermined set (0V, 5V).

Analog voltages and currents are used to directly control something, such as the volume of a car radio. On a simple radio, the volume control is connected with a variable resistor. Turn the knob to increase or decrease the resistance. At this moment, the amount of current flowing through the resistor also increases or decreases. This increases or decreases the volume. Analog circuits, like radios, have a linear output proportional to the input.

However, just because analog control looks intuitive and simple doesn't always make it economically attractive or practical. As an example, analog circuits are constantly changing over time and are very difficult to modify. Sophisticated analog circuits that solve this problem are also large, heavy or expensive, and generate a lot of heat.

Power consumption is proportional to the product of the current flowing through the connected equipment and the voltage between them. Analog circuitry can also be noise sensitive due to unrestricted resolution. Even the smallest fluctuations in the analog signal change the value.

Compared to pure analog control, controlling analog circuits through digitalization can drastically reduce the cost and power consumption of the system. Many microcontrollers and digital signal processors (DSPs) already have a built-in PWM controller that facilitates implementation.

In other words, PWM is a method of digitizing and encoding analog signals. With a high resolution counter, the duty cycle of the square wave is modulated to encode a particular analog signal. Since the DC power supply is ON or OFF, at any given time the PWM signal is still a digital signal. Voltage or current is supplied to the analog device through a series of repeated ON and OFF pulses. The ON section refers to the period during which DC power is supplied to the analog device, and the OFF section refers to the period during which the power supply switch is shut off. If enough bandwidth is given, any analog value can be encoded via PWM. By simply adjusting the duty cycle of this PWM signal, it is possible to control the analog signal. For example, if the supply is powered at 9V and the duty cycle is 10%, the resulting analog signal is 0.9V.

As described above, a technique for controlling an analog system using PWM is used in various industrial fields such as an electric system and a mechanical system. In particular, PWM is widely used to drive a motor (rotary motor, linear motor, etc.) which is one of the analog mechanical systems. The PWM used in the conventional motor driving is somewhat different depending on the driving method, but it has remained to perform a simple motor driving by the forward rotation, reverse rotation, and pause using a fixed pulse width. For example, a duty cycle of 25% means a constant speed forward rotation of the motor, 75% a constant speed reverse rotation of the motor, and 50% means a pause of the motor.

However, the conventional simple motor drive control technique is not sufficient in a field requiring various and precise control techniques for driving the motor according to changes in external input such as a camera shake correction device and a motion control device of a mobile robot.

It is an object of the present invention to provide a method and apparatus capable of controlling various motor driving using PWM.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above technical problem, according to an embodiment of the present invention, a motor control device for controlling the movement of the motor using PWM, the motor for generating a predetermined movement; A position sensor for sensing a sensor value relating to a current position of the motor; A control decision loop for comparing the sensor value with a target value to obtain an error value; A pulse adjusting unit for adjusting the pulse width and the number of pulses of the PWM signal according to the obtained error value; And a motor driver for driving the motor by power input to the motor based on the adjusted PWM signal.

In order to achieve the above technical problem, according to an embodiment of the present invention, a motor control method for controlling the movement of the motor using PWM, the step of sensing a sensor value relating to the current position of the motor; Obtaining an error value by comparing the sensor value with a target value to be controlled; Adjusting the pulse width and the number of pulses of the PWM signal according to the obtained error value; And driving the motor by power input to the motor based on the adjusted PWM signal.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a motor driving method by pulse width control according to a first embodiment of the present invention. In the first embodiment, when driving the motor and controlling the speed thereof, the pulse width is calculated according to the difference between the current position value detected from the motor and the position value intended by the user (hereinafter referred to as an error value). It is a method of changing the speed of a motor by changing a pulse width. In other words, if the error value is large, the motor speed is faster to reduce the error value, and if the error value is small, the motor speed is slower to precisely and accurately control the position of the motor.

Referring to FIG. 1, the pulse width of the next pulse 12 is greater than the pulse width of the initial pulse 11 of the PWM signal A. This increases the pulse width to reduce the error value more quickly to reach the target position when the error value is larger in the next state than in the initial state. The PWM signal A 'is a signal having a reverse phase with the PWM signal A, and is input in pairs to two terminals of the motor driver 170 as shown in FIG. As a method of inputting the reverse phase PWM signals, the PWM signal A is input to the first terminal of the motor driver 170, and the PWM signal A is inverted by the inverter 21 to invert the reverse phase PWM signal. A method of generating A 'and then inputting it to the second terminal of the motor driver 170 may be used.

The motor driver 170 may control the operation of the motor 180 by switching the power supply 160 according to the input PWM signal. For example, the motor driver 170 switches so that the power supply 160 flows into the motor 180 only during a section of the PWM signal A that is HIGH.

In FIG. 2, the inverter 21 is used to generate a signal that is inverse of the original PWM signal. However, this is only an example. In addition to the signal generating device for generating the original PWM signal, an additional signal generating device may be provided to generate a reverse phase signal of the original PWM signal.

3 is a view showing a motor driving method by pulse number control according to a second embodiment of the present invention. In the second embodiment, when the motor is driven and the movement amount (displacement) is to be controlled, the movement amount of the motor is changed by calculating the number of pulses according to the error value and changing the number of pulses. That is, if the error value is large, the number of pulses is increased to increase the amount of movement of the motor. If the error value is small, the number of pulses is reduced to reduce the amount of movement of the motor.

Referring to FIG. 3, there may be up to N pulses within a period of the PWM signal. The user can then adjust the amount of movement of the motor by selecting the appropriate number of pulses from 1 to N within the period. If the error value increases as time passes, the movement amount can be increased by appropriately increasing the number of pulses as shown in FIG. 3. Of course, on the contrary, if the error value decreases with time, the movement amount can be reduced by appropriately reducing the number of pulses. In FIG. 3, the PWM signal A and the PWM signal A 'have opposite phases, and are input in pairs to two terminals of the motor driver 170.

As shown in FIG. 4, the pulse width control means forward rotation when the duty cycle of the pulse is smaller than 50% and reverse rotation when it is larger than 50%. For example, a pulse with a duty cycle of 25% and a pulse with a duty cycle of 75% mean that the motor is rotated at opposite speeds and at the same magnitude.

5 is a view showing a motor driving method by controlling the pulse width and the number of pulses according to the third embodiment of the present invention. In the third embodiment, when driving the motor and controlling the speed and the moving amount together, the pulse width and the pulse number are calculated according to the error value, and the speed and the moving amount of the motor are changed by varying the pulse width and the pulse number. How to change. That is, in the third embodiment, the speed of the motor is controlled by the pulse width and the amount of movement of the motor is controlled by the number of pulses, which can be regarded as a combination of the first and second embodiments.

Referring to FIG. 5, as shown in FIG. 3, the number of pulses is changed from three to five, and the pulse width of each pulse is also reduced (w ₁ ) or stretched (w ₂ ). In this way, more precise and efficient motor control is possible by controlling the speed of the motor with the variable pulse width and controlling the amount of movement of the motor with the variable pulse number.

For example, if the error value is large, the pulse width can be widened to increase the speed of the motor to increase the number of pulses and the motor movement amount, thereby reducing the error value in a shorter time. Instead of slowing down speeds and reducing the number of pulses, you get more precise control.

In FIG. 5, the PWM signal A and the PWM signal A 'have opposite phases, and are input in pairs to two terminals of the motor driver 170.

6 is a view showing a motor driving method by a branch signal according to a fourth embodiment of the present invention. In the fourth embodiment, when the speed and position of the motor are controlled by driving the motor, the pulse width and the number of pulses of the PWM signal are varied to control the speed and position of the motor. This is a method of multiplying a branch signal of frequency by a gate (eg, an AND gate). Since the fourth embodiment can control by dividing the PWM driving signal, the control cycle can be changed, thereby reducing noise and vibration. In general, one of the important aspects of a device's ability to generate a PWM signal pulse is the pulse generation period. The better the device, the shorter the period that can change the pulse, so it is possible to control the motor operation by generating different pulses for each short period. However, the higher the performance of the pulse generator, the higher the cost. Therefore, according to the fourth embodiment of the present invention, even if the period in which the pulse generator is able to change the pulse is fixed, the branch signal can be used for the branch signal. Shorter periods of motor control are possible.

As shown in FIG. 6, if there is a PWM signal A having a specific period, and there is a branch signal B having a smaller period, the number of pulses is less than the specific period by multiplying the two signals A and B. Can be controlled.

On the other hand, as shown in Fig. 7, it is also possible to change the pulse width using the branch signal. Referring to FIG. 7, not only the number of pulses of the PWM signal A uniformly generated at a specific period may be selected by the branch signal B but also the pulse width may be finely adjusted.

For example, any of the branch signals B 62 may appropriately reduce the width of the pulse 61. Thus, the speed of the motor can be finely controlled by finely adjusting the pulse 61 present at the boundary of the branch signal B. In this case, the PWM signal A itself consists of the same pulses, but the branch signal B allows the adjustment of the number of pulses and the fine adjustment of the pulse width.

In the above embodiments, as shown in FIG. 4, when the PWM signal input based on the 50% duty ratio of the PWM signal is smaller than this, the motor 180 is controlled to rotate in the first direction. It has been described that 180 is controlled to rotate in the second direction (the direction opposite to the first direction).

By the way, when the motor 180 rotates at a certain speed in the forward direction, and when the motor 180 rotates at the speed in the reverse direction, it has a structure that is physically symmetric with each other. However, according to the control scheme as shown in FIG. 4, for example, the duty ratio for causing the motor 180 to rotate at a specific speed in the forward direction is 25%, for the motor 180 to rotate at the same speed in the reverse direction. Duty ratio is 75%. Therefore, such a control method does not achieve a physical symmetry structure, so oscillation may occur due to unbalance when switching between forward and reverse directions, and asymmetric wear may occur when used for a long time.

Considering this point, as shown in Fig. 8, the duty ratio (D) of the PWM signal always controls the magnitude of the speed according to the pulse width at 50% or less, but the direction of rotation depends on which terminal the PWM signal is input. The embodiment determined by this can be considered.

According to the above embodiment, for example, when the PWM signal having a duty ratio of 25% is input to the first terminal A of FIG. 2, the motor 180 rotates in the forward direction at a specific speed, and the second terminal A ' When a PWM signal having a duty ratio of 25% is input to the motor, the motor 180 rotates in the reverse direction at the same speed. Of course, at this time, the signal opposite to the PWM signal is input to the terminal opposite to the terminal to which the PWM signal is input.

According to this embodiment, the pulse width of the PWM signal is limited to less than half, the forward and reverse control of the motor 180 is possible, and the physical symmetry of the motor 180 can be maintained.

9 is a diagram illustrating the configuration of the motor control apparatus 100 according to an embodiment of the present invention. The motor control apparatus 100 includes the A / D converter 110, the signal processor 120, the control decision loop 130, the oscillator 140, the pulse controller 150, the power supply 160, and the motor driver 170. It may be configured to include a motor 180 and a position sensor 190.

The position sensor 190 provides the A / D converter 100 with a detection signal regarding the current position of the motor 180 based on the detection signal from the predetermined position detection element. The position detecting device may be made of, for example, a Position Sensitive Device (PSD).

The A / D converter 110 receives a detection signal (analog) of the position sensor 190 and converts it to a digital value.

The signal processor 120 performs predetermined filter processing or integration processing on the converted digital value, and inputs the processed result (processed sensor value) to the control decision loop 130.

The control decision loop 130 compares the sensor value processed by the signal processor 120 with a target position to be controlled to obtain an error value. However, the error value does not have to be completely zero, and the predetermined error value set in advance may be a target value. For example, the error value may be obtained according to an operation divided by a servo period. The control decision loop 130 may additionally perform initialization functions such as user-defined register declaration, interrupt vector definition, and internal configuration register setting.

On the other hand, from a hardware point of view, the control decision loop 130 reads and executes a ROM (Read Only Memory) for storing a control program and the like, a Random Access Memory (RAM) for temporarily storing data, and the control program and the like from the ROM. CPU (Central Processing Unit) or the like. If the error value is large, the control decision loop 130 controls the pulse controller 150 to have a high speed and a large amount of movement of the motor 180.

The pulse controller 150 receives the basic pulse wave generated from the oscillator 140 and based on the error value provided from the control decision loop 130, according to the first to third embodiments of the present invention. The pulse width and / or number of pulses of the pulse wave are adjusted and a PWM signal is generated. In addition, as in the fourth embodiment of the present invention, the pulse adjusting unit 150 connects the branch signal having a frequency lower than the frequency of the fundamental pulse wave to the PWM signal whose pulse width and / or pulse number are adjusted by a gate. More specifically, the pulse controller 150 may include a pulse width controller 151 for adjusting the pulse width of the fundamental pulse wave to change the rotational speed of the motor 180. In order to change the amount of movement of the motor 180, a pulse number adjusting unit 152 for adjusting the number of pulses of the basic pulse wave, and a branch signal for obtaining a product of a PWM signal and a branch signal in which the pulse width and / or number of pulses are adjusted. The application unit 153 may be configured.

The pulse controller 150 provides the finally adjusted PWM signal and its inverted signal to the motor driver 170. In order to invert the PWM signal, the pulse controller 150 may further include a predetermined inverter.

Meanwhile, as described in the embodiment of FIG. 8, the pulse controller 150 controls the motor to rotate in the forward direction by inputting the PWM signal to the first terminal of the motor driver, and controls the PWM signal to the motor. Input to the second terminal of the driver may be controlled to rotate the motor in the reverse direction.

The motor driver 170 switches the power supply 160 based on the PWM signal provided from the pulse adjusting unit 150. For example, in a section in which the PWM signal is high, the power supply 160 is provided to the motor 180 by closing the switch, and in a section in which the PWM signal is low, the power supply 160 is provided to the motor 180 by opening the switch. Do not The motor driver 170 may be formed of, for example, a bridge circuit formed from a predetermined number of switch elements (for example, N-channel or P-channel FETs).

The motor 180 receives the power 160 under the control of the motor driver 170 and performs a predetermined movement. The motor 180 includes various motors and various actuators known in the art, such as rotary motors, linear motors, step motors, and the like.

Until now, each block in FIG. 9 is a software, such as a task, a class, a subroutine, a process, an object, an execution thread, a program, or a field-programmable gate array (ASIC) or an application (ASIC) that is performed in a predetermined area of memory. It may be implemented in hardware, such as a -specific integrated circuit, or may be a combination of the above software and hardware. The blocks may be included in a computer-readable storage medium or a part of the blocks may be distributed among a plurality of computers.

In addition, each block may represent a module, segment or portion of code that includes one or more executable instructions for executing a specified logical function. It is also possible in some alternative embodiments that the functions mentioned in the blocks occur out of order. For example, the two blocks shown in succession may in fact be executed substantially concurrently, and the blocks may sometimes be executed in the reverse order, depending on the corresponding function.

10 is a flowchart illustrating a motor control method 100 according to an embodiment of the present invention.

First, the control decision loop 130 initializes a user-defined register declaration, an interrupt vector definition, and an internal configuration register setting (S10).

When the motor 180 is driven, the position sensor 190 detects a sensor value regarding the current position of the motor 180 (S20). Then, the A / D converter 110 digitizes the sensed sensor value (S30), and the signal processor 120 applies a filter such as an integral process to the digitized sensor value (S40).

The control decision loop 130 obtains an error value by comparing the sensor value filtered by the signal processor 120 with a target value to be controlled (S50), and the pulse controller 150 controls the PWM signal according to the obtained error value. The pulse width and the number of pulses are adjusted (S60). Specifically, the pulse width adjusting unit 151 included in the pulse adjusting unit 150 adjusts the pulse width of the PWM signal to change the rotational speed of the motor 180, and the pulse number adjusting unit 152 The number of pulses of the PWM signal may be adjusted to change the movement amount of the motor 180.

In addition, the branch signal applying unit 153 included in the pulse controller 150 performs an operation for obtaining a product of the PWM signal and a branch signal having a frequency smaller than the frequency of the PWM signal (S70). This operation may be performed by connecting the PWM signal and the branch signal to a gate.

The branch signal applying unit 153 may adjust the number of pulses overlapping the branch signal among the PWM signals in order to control the movement amount of the motor 180, and finely adjust the speed of the motor 180. In order to control, the width of the pulse present in the boundary portion of the PWM signal may be adjusted. The width of the pulse present in the boundary portion can be adjusted, as shown in Figure 7, the portion overlapped by the operation of the PWM signal and the branch signal includes a portion 63 of a certain pulse 61 Because you can.

Finally, the motor driver 170 drives the motor by the power input to the motor based on the adjusted PWM signal (S80). At this time, the signal input to the motor driver 170 is a pair of the adjusted PWM signal and the reverse phase signal of the adjusted PWM signal. The reversed phase signal may be generated by inverting the regulated PWM signal through an inverter.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the present invention, there is an advantage in that the speed and position of the motor can be controlled in various ways using PWM.

In addition, according to the present invention, there is an advantage that the motor can be precisely controlled in units of a period smaller than the period of the basic PWM signal.

Claims (22)

In the motor control device for controlling the movement of the motor by using pulse width modulation (PWM), A motor for generating a predetermined movement; A position sensor for sensing a sensor value relating to a current position of the motor; A control decision loop for comparing the sensor value with a target value to obtain an error value; A pulse adjusting unit for adjusting the pulse width and the number of pulses of the PWM signal according to the obtained error value; And And a motor driver for driving the motor by power input to the motor based on the adjusted PWM signal. The method of claim 1, wherein the motor Motor control device which is any one of rotary motor, linear motor, step motor and actuator. According to claim 1, wherein the pulse control unit A pulse width adjusting unit for adjusting a pulse width of the PWM signal to change the rotational speed of the motor; And And a pulse number controller for adjusting the number of pulses of the PWM signal to change the amount of movement of the motor. According to claim 1, wherein the pulse control unit And a branch signal application unit for obtaining a product of the PWM signal and a branch signal having a frequency smaller than a frequency of the PWM signal. According to claim 1, wherein the pulse control unit A motor control device for controlling the motor to rotate in the reverse direction by inputting the PWM signal to the first terminal of the motor driver to control the motor to rotate in the forward direction, and inputting the PWM signal to the second terminal of the motor driver. . The method of claim 4, wherein the branch signal applying unit And the PWM signal and the branch signal are connected to gates to obtain the product. The method of claim 4, wherein the pulse control unit In order to control the amount of movement of the motor, the motor control device for adjusting the number of pulses overlapping the branch signal of the PWM signal The method of claim 4, wherein the pulse control unit In order to finely control the speed of the motor, the motor control device for adjusting the width of the pulse present in the boundary portion of the PWM signal. The method of claim 1, wherein the motor driver Motor control device for receiving the adjusted PWM signal and the reversed phase signal of the adjusted PWM signal in pairs 10. The method of claim 9, wherein the reversed phase signal is And a motor inverting the adjusted PWM signal through an inverter. The method of claim 1, An A / D converter for digitizing the sensed sensor value; And And a signal processor configured to apply a filter to the digitized sensor values. In the motor control method for controlling the movement of the motor using pulse width modulation (PWM), Detecting a sensor value relating to a current position of the motor; Obtaining an error value by comparing the sensor value with a target value to be controlled; Adjusting the pulse width and the number of pulses of the PWM signal according to the obtained error value; And And driving the motor by power input to the motor based on the adjusted PWM signal. The method of claim 12, wherein the motor A motor control method which is any one of a rotary motor, a linear motor, a step motor and an actuator. The method of claim 12, wherein the adjusting step Adjusting the pulse width of the PWM signal to change the rotational speed of the motor; And And adjusting the number of pulses of the PWM signal to change the amount of movement of the motor. The method of claim 12, wherein the adjusting step Obtaining a product of the PWM signal and a branch signal having a frequency smaller than a frequency of the PWM signal. The method of claim 12, wherein the adjusting step Controlling the motor to rotate in a forward direction by inputting the PWM signal to a first terminal of the motor driver; And Inputting the PWM signal to the second terminal of the motor driver to control the motor to rotate in the reverse direction. The method of claim 15, wherein the adjusting is Connecting the PWM signal and the branch signal to a gate to obtain the product. The method of claim 15, wherein the adjusting is And controlling the number of pulses overlapping with the branch signal among the PWM signals to control the amount of movement of the motor. 19. The method of claim 18, wherein adjusting And controlling a width of a pulse present at a boundary of the PWM signal to finely control the speed of the motor. The method of claim 12, wherein the driving step The motor control method comprising the step of receiving the adjusted PWM signal and the reversed phase signal of the adjusted PWM signal in pairs 21. The method of claim 20, wherein the reversed phase signal is And a motor inverting the adjusted PWM signal through an inverter. The method of claim 12, Digitizing the sensed sensor value; And And applying a filter to the digitized sensor values.

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