Motor control device without position sensor

Abstract

A motor control device without a position sensor mainly comprises a main power circuit and a control circuit, and the main power circuit is used for providing an energy source for directly driving a motor to run, is a high-voltage large-current circuit and is controlled by the control circuit; and the control circuit is a software operation platform and is used for carrying out ADC sampling on the voltage and the current output by the main power circuit, resolving the position information of the motor rotor and carrying out on-off control on the main power circuit based on the resolved position information. Compared with a traditional encoder for position feedback, the device has the advantages that the size, weight and hardware cost of a motor control system are saved, the stability of the system can be effectively improved in a severe environment, meanwhile, compared with traditional motor open-loop control, closed-loop control over the system can be achieved, and the response speed and the control precision are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a sensorless motor control device. Background Technology

[0002] When using a field-oriented control drive motor, in order to achieve a high-performance three-phase PMSM (Permanent Magnet Synchronous Motor) control system, it is generally necessary to collect the accurate position and speed of the rotor as feedback quantities for the motor system.

[0003] Existing technologies typically use incremental or absolute encoders to provide position and speed information in motor control. However, the installation and use of commonly used mechanical sensors can lead to increased costs, larger motor size, and the need for physical correction of the rotor's initial position. In addition, encoders have strict requirements for the operating environment. For example, encoders may fail in strong magnetic or strong vibration environments, reducing system reliability.

[0004] Sensorless control technology detects relevant electrical signals in the motor windings and uses control algorithms to calculate the actual position and speed of the rotor, representing the development trend of three-phase PMSM control systems. However, most current sensorless controls use open-loop control, resulting in slow system response and low accuracy. Summary of the Invention

[0005] This disclosure provides a sensorless motor control system that effectively reduces costs and improves system reliability in harsh environments. The platform is designed with a DSP as the processor. The DSP uses the Haver architecture, where the microprocessor's data bus and instruction bus are separated, resulting in higher execution efficiency and faster speed compared to von Neumann architecture microprocessors.

[0006] The basic idea of ​​sensorless control is to superimpose a high-frequency voltage or current signal onto a modulated wave signal, modulate it using SVPWM (Space Vector Pulse Width Modulation), and then apply it to the motor load via a switching transistor. The high-frequency voltage or current signal is extracted from the motor current, and the rotor position information is calculated. Then, the motor is controlled based on the calculated position information.

[0007] The block diagram of the sensorless control system for a three-phase PMSM based on rotating high-frequency voltage signal injection is as follows: Figure 1 As shown.

[0008] Injecting an orthogonal high-frequency signal of formula (1) into a stationary coordinate system (1) in, and These are the amplitude and angular frequency of the injected signal.

[0009] The differential of the high-frequency current response after injection is shown in equation (2).

[0010] (2) in: Rotor angle, cross saturation angle

[0011] ,

[0012] Based on the above equation, the high-frequency current response in the stationary coordinate system can be derived as follows: (3) (4) in

[0013] The injected high-frequency voltage signal and current response are represented by a negative vector as follows: (5) (6) The high-frequency current response shows that the negative sequence component... Contains rotor component Therefore, the rotor position can be determined from the negative sequence current component. Extract from.

[0014] Will , Perform the following calculations: (7) in To obtain the observed rotor angle, in equation (7) For high-frequency components, The DC component is obtained by filtering out the high-frequency components using a low-pass filter. .

[0015] make ; Actual value of rotor Compared with observed values The difference between them. Define the function. for (8) Through the observer ( Figure 2 As shown), By adjusting to zero (based on closed-loop control of the PI controller), the rotor angle can be estimated. The rotor position estimation demodulation method is as follows: Figure 2 As shown.

[0016] The analysis process in the above figure is as follows: When When >0, that is > ,at this time >0, After passing through the PI controller and integral calculation Increase Decrease until Approaching 0, The same logic applies to cases where the value is less than 0.

[0017] When selecting a high-frequency carrier signal, the signal-to-noise ratio and the disturbance caused by the high-frequency signal need to be considered. Usually, the amplitude of the injected signal is set to 0.1 times the rated voltage and the frequency is 0.1 times the switching frequency.

[0018] In this disclosure, the input current of the motor is acquired through a sampling circuit. After (e.g.) Figure 3 As shown in the figure, based on the above calculation method, the rotor position angle and speed information of the motor are estimated by collecting the current value, which replaces the encoder function and realizes sensorless control of the motor.

[0019] Specifically, the sensorless motor control device provided in this disclosure mainly includes: a main power circuit and a control circuit, wherein, Main power circuit: Used to provide the energy source for directly driving the motor, it is a high-voltage, high-current circuit and is controlled by the control circuit; Control circuit: This is a software platform used to sample the voltage and current output by the main power circuit using an ADC, calculate the motor rotor position information, and control the switching of the main power circuit based on the calculated position information.

[0020] Furthermore, the power supply type of the main power circuit includes: DC power supply: When the power supply is DC, the DC power supply drives the motor to run by switching 6 switching transistors; the switching transistors are IGBTs or MOSFETs; AC power supply: When the power supply is AC, the AC power is first rectified into DC power, and the DC power drives the motor to run by switching 6 switching transistors.

[0021] Furthermore, the control circuit includes: a motor current sampling module, a control module with a DSP as the main control chip, and a switching transistor drive circuit module; wherein: The control module, with DSP as the main control chip, collects the three-phase current and DC bus voltage of the motor through peripheral devices and external circuits. It uses these as loop calculation inputs and calculates the angle and speed information of the motor rotor based on the current value after collecting the three-phase current. The calculated rotor angle and speed, along with the acquired current value, are used together as feedback values ​​for loop calculation. The loop control calculates the duty cycle of each switch, and the drive circuit uses this to drive the switches on and off, thus achieving closed-loop control of the motor.

[0022] Furthermore, the method by which the control module calculates the motor rotor position information includes: Collect the motor drive three-phase current output from the main power circuit; The high-frequency components are filtered out by a low-pass filter to obtain the DC component. ; make ; Actual value of rotor Compared with observed values The difference between them; Define function for

[0023] Through closed-loop regulation based on a PI controller, Adjust to zero and estimate the rotor angle. .

[0024] Furthermore, the ADC sampling and control timing of the control circuit includes: The ePWM module configured in the DSP generates a triangular wave by counting up and down. The ADC sampling is triggered at the peak of the triangular wave, at which point the motor current is the average current value. When the triangular wave reaches its trough, the loop calculation begins. At this time, the DSP's main control chip processes the input ADC sampled value to obtain the rotor position and speed information, performs motor control loop calculation, and obtains the new duty cycle. At the next valley value, the motor duty cycle is updated to the calculated duty cycle, and the drive circuit drives the switching transistor to turn on and off according to the updated duty cycle.

[0025] Furthermore, when it is necessary to increase the system bandwidth, the main control chip is replaced with an FPGA, and the ADC sampling and control timing is changed from single sampling and single update to double sampling and double update. That is, in each switching cycle, sampling, loop calculation, and duty cycle update are performed once every half cycle.

[0026] Furthermore, the control circuit also includes a protection circuit to prevent overcurrent, overtemperature, and overvoltage, used to quickly shut down the PWM in case of overcurrent, overvoltage, or overtemperature. When the detected motor current, bus current, DC voltage, or switching device temperature exceeds the set value, a low level is output through a comparator or operational amplifier to generate a TZ event signal, triggering the PWM output to turn off.

[0027] Furthermore, the control circuit also includes a communication module for communicating with the upper-level device, receiving control commands from the upper-level device, and uploading operating conditions to the upper-level device.

[0028] Compared with the prior art, the beneficial effects of this disclosure are: ① Compared with traditional encoders for position feedback, this disclosure saves the size, weight and hardware cost of the motor control system, and can effectively improve the stability of the system in harsh environments such as strong impact or strong magnetic fields, avoiding system failures caused by encoder failure; ② Compared with traditional open-loop motor control, the calculation of rotor angle and speed in this disclosure can realize closed-loop control of the system, effectively improving response speed and control accuracy; ③ It has the function of quickly shutting down PWM in case of overcurrent or overvoltage; ④ It has good economic and practical value. Attached Figure Description

[0029] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments of this disclosure taken in conjunction with the accompanying drawings, in which the same reference numerals generally represent the same components.

[0030] Figure 1 This is a block diagram of a sensorless control system for a three-phase PMSM based on rotating high-frequency voltage signal injection. Figure 2 This is a rotor position estimation and demodulation method based on the injection of a rotating sinusoidal signal; Figure 3 This is a schematic diagram of the main circuit and control circuit of the motor control platform. Figure 4 Flowchart for program initialization; Figure 5 For ADC sampling and control timing (single sampling, single update); Figure 6 shows the ADC sampling and control timing (double sampling and double update). Figure 7 is a schematic diagram of the TZ protection principle; Figure 8 This is an example of a main power circuit topology (power supply is DC). Figure 9 This is an example of a main power circuit topology (power supply is AC). Detailed Implementation

[0031] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0032] This disclosure provides a sensorless motor control device that effectively reduces costs and improves system reliability in harsh environments. The platform is designed with a DSP as the processor. The DSP uses the Haver architecture, where the microprocessor's data bus and instruction bus are separated, resulting in higher execution efficiency and faster speed compared to von Neumann architecture microprocessors.

[0033] In one exemplary implementation: like Figure 3 As shown, current is collected through a sampling circuit. Then, the motor rotor position angle and speed information are estimated by collecting the current value, replacing the encoder function and realizing sensorless control of the motor.

[0034] In this embodiment, Figure 3 The motor control platform shown is divided into a main power circuit and a control circuit. The left side (outside the dashed box) is the main power circuit, and the area inside the dashed box is the control circuit. Main power circuit: The energy (power) source that directly drives the motor, is a high-voltage, high-current circuit, and is controlled by the control circuit; Control circuit: The software platform samples the voltage and current of the main power circuit to achieve switching control and protection control of the main power circuit. It also communicates with the upper-level equipment, receiving control commands (start, stop, speed setting, etc.) and uploading operating conditions (motor operating current, operating speed, etc.) to the upper-level equipment. 1. Main power circuit It consists of a DC regulated power supply (if the power supply is AC, the first stage passes through a rectifier, in which case the DC terminal is a voltage regulator capacitor), 6 IGBT modules (or MOSFETs), a permanent magnet synchronous motor, etc. See attached... Figure 8 and ９ As shown, the main power circuit is divided into the following two categories according to the power supply type: 1) DC power supply: When the power supply is DC, the DC power supply drives the motor to run by switching on and off 6 IGBT modules (or MOSFETs); 2) AC power supply: When the power supply is AC, the AC power is first converted into DC power through uncontrolled rectification or fully controlled rectification. The DC power drives the motor to run by switching on and off 6 IGBT modules (or MOSFETs). 2. Control Circuit In this embodiment, the control circuit includes: a motor current ADC sampling circuit, a DSP as the main control chip control circuit, and an IGBT (MOS) drive circuit; in addition, preferably, it also includes: a protection circuit to prevent overcurrent, overtemperature and overvoltage and a communication circuit, etc.

[0035] (1) In this embodiment, the process of controlling the motor can be described as follows: The control circuit with DSP as the main control chip collects the three-phase current of the motor and the DC bus voltage through peripheral devices and external circuits, and uses these as loop calculation inputs and protection circuit inputs. After acquiring the three-phase current, the angle and speed information of the motor rotor are calculated based on the current value. The calculation algorithm replaces the function of the traditional encoder. The calculated rotor angle and speed, along with the collected current value, can be used as feedback values ​​for loop calculation. The loop control calculates the duty cycle of each switch, and the drive circuit drives the switches to turn on and off according to the duty cycle, thus realizing closed-loop control of the motor.

[0036] The motor operating modes are divided into position control, speed control, and torque control. When the motor operates in position mode, the motor control loop, from the outside in, consists of a position loop, a speed loop, and a current loop. When the motor operates in speed mode, the motor control loop, from the outside in, consists of a speed loop and a current loop. When the motor operates in torque mode, the motor control loop is a single current loop. After the loop calculations are completed, a modulation wave is obtained. Based on the modulation wave, different duty cycles are output using the DSP's internal software. Different duty cycles determine different conduction times for the IGBT module (MOSFET), thus achieving motor control.

[0037] (2) In this embodiment, all DSP function functions (including clock, timer, ePWM initialization configuration functions, interrupt service functions, etc.) are run based on the controller peripheral module. Therefore, the peripheral is initialized and configured first when powered on or reset. The overall initialization function configuration of the motor controller is shown in Figure 4.

[0038] After the program is initialized and configured, ADC sampling (motor current sampling), loop calculation, and duty cycle update are all triggered by ePWM. ePWM (Enhanced Pulse Width Modulation) is a dedicated hardware peripheral integrated in the DSP / MCU. Its core function is to generate high-precision, programmable PWM waveforms and provide enhanced functions such as dead-time control, fault protection, and synchronous triggering.

[0039] Figure 5 shows the ADC sampling and control timing: The ADC sampling is triggered at the peak of the triangular wave (in Figure 5, the triangular wave is generated by the time base submodule of the DSP's ePWM module using an increment / decrement counting mode), and the motor current at this time is the average current value. When the triangular wave reaches its trough, the loop calculation begins. At this point, the main control chip processes the input ADC sampled value to obtain the rotor position and speed information, and performs motor control loop calculation to obtain a new duty cycle. The duty cycle calculated at the next valley value is then used by the drive circuit to turn the switching transistor on and off.

[0040] Specifically, when the counter counts down to 0, an interrupt is triggered by the action-limiting submodule. Within the interrupt service function, the most recently calculated CMPx value can be updated, which is equivalent to updating the duty cycle. Taking the first bridge arm of a three-phase bridge as an example, the duty cycle is the ratio of the on-time (high level) of the upper transistor to the switching cycle. When the drive circuit receives a high level, it will drive the switching transistor to turn on; when the drive circuit receives a low level, it will drive the switching transistor to turn off. That is, the duty cycle can determine the on-time of the switching transistor IGBT (MOSFET) within one switching cycle.

[0041] The loop calculation process requires different clock cycles depending on the amount of computation. Therefore, during the program cycle setting process, it is necessary to ensure that the running time of the interrupt program does not exceed the cycle value of the ePWM module. Otherwise, the next interrupt will be suspended, affecting the stability of the program.

[0042] When increased system bandwidth is required, the main control chip can be replaced with an FPGA, and the ADC sampling and control timing can be modified from single-sample, single-update to double-sample, double-update. This improves the control loop speed and reduces system latency. Figure 5 shows the time taken from triggering sampling to updating the duty cycle. That is, the delay time is The double sampling and double update are shown in Figure 6, which shows the time taken from triggering sampling to updating the duty cycle. That is, the delay time is The lower the latency, the higher the bandwidth.

[0043] (3) In this embodiment, the motor control system has an overcurrent and overvoltage fast PWM shutdown function (ePWM module). When the detected motor current, bus current, DC voltage, or switching device temperature exceeds the set value, a TZ event signal is generated, triggering the PWM output to shut down. Taking the motor current as an example, the TZ protection principle diagram is shown in Figure 7.

[0044] When the sampled current is lower than the reference value, the voltage comparator outputs a high level, and the control system is in normal operation. When the sampled current is higher than the reference value, the operational amplifier outputs a low level. The TZ pin is low, triggering a protection action and shutting down the PWM output.

[0045] The above technical solutions are merely exemplary embodiments of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the specific embodiments of the present invention. Therefore, the methods described above are merely preferred and not restrictive.

Claims

1. A sensorless motor control device, characterized in that, include: The main power circuit and control circuit, among which, Main power circuit: Used to provide the energy source for directly driving the motor, it is a high-voltage, high-current circuit and is controlled by the control circuit; Control circuit: This is a software platform used to sample the voltage and current output by the main power circuit using an ADC, calculate the motor rotor position information, and control the switching of the main power circuit based on the calculated position information.

2. The apparatus according to claim 1, characterized in that, The power supply types of the main power circuit include: DC power supply: When the power supply is DC, the DC power supply drives the motor to run by switching 6 switching transistors; the switching transistors are IGBTs or MOSFETs; AC power supply: When the power supply is AC, the AC power is first rectified into DC power, and the DC power drives the motor to run by switching 6 switching transistors.

3. The apparatus according to claim 2, characterized in that, The control circuit includes: a motor current sampling module, a control module with a DSP as the main control chip, and a switching transistor drive circuit module; wherein: The control module, with DSP as the main control chip, collects the three-phase current and DC bus voltage of the motor through peripheral devices and external circuits. It uses these as loop calculation inputs and calculates the angle and speed information of the motor rotor based on the current value after collecting the three-phase current. The calculated rotor angle and speed, along with the acquired current value, are used together as feedback values ​​for loop calculation. The loop control calculates the duty cycle of each switch, and the drive circuit uses this to drive the switches on and off, thus achieving closed-loop control of the motor.

4. The apparatus according to claim 3, characterized in that, The method by which the control module calculates the motor rotor position information includes: Collect the motor drive three-phase current output from the main power circuit; The high-frequency components are filtered out by a low-pass filter to obtain the DC component. ; make ; Actual value of rotor Compared with observed values The difference between them; Define function for Through closed-loop regulation based on a PI controller, Adjust to zero and estimate the rotor angle. .

5. The apparatus according to claim 3, characterized in that, The ADC sampling and control timing of the control circuit includes: The ePWM module configured in the DSP generates a triangular wave by counting up and down. The ADC sampling is triggered at the peak of the triangular wave, at which point the motor current is the average current value. When the triangular wave reaches its trough, the loop calculation begins. At this time, the DSP's main control chip processes the input ADC sampled value to obtain the rotor position and speed information, performs motor control loop calculation, and obtains the new duty cycle. At the next valley value, the motor duty cycle is updated to the calculated duty cycle, and the drive circuit drives the switching transistor to turn on and off according to the updated duty cycle.

6. The apparatus according to claim 3, characterized in that, When it is necessary to increase system bandwidth, the main control chip is replaced with an FPGA, and the ADC sampling and control timing is changed from single sampling and single update to double sampling and double update. That is, in each switching cycle, sampling, loop calculation and duty cycle update are performed once every half cycle.

7. The apparatus according to any one of claims 1-6, characterized in that, The control circuit also includes a protection circuit to prevent overcurrent, overtemperature, and overvoltage, used to quickly shut down the PWM in case of overcurrent, overvoltage, or overtemperature. When the detected motor current, bus current, DC voltage, or switching device temperature exceeds the set value, a low level is output through a comparator or operational amplifier to generate a TZ event signal, triggering the PWM output to turn off.

8. The apparatus according to claim 7, characterized in that, The control circuit also includes a communication module, used to communicate with the upper-level device, receive control commands from the upper-level device, and upload operating conditions to the upper-level device.

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