A BLDCM control system based on a new approaching rate sliding mode variable structure control

Abstract

The present invention discloses a brushless DC motor (BLDCM) control system based on a novel reaching-rate sliding-mode variable structure control. The method is applicable to the field of BLDCM control. The control system includes a sliding-mode variable structure controller, a PWM modulation unit, an inverter unit, a brushless DC motor, and a position sensor unit. The sliding-mode variable structure controller applies a sliding-mode variable structure control algorithm to the position control of the BLDCM and employs a novel reaching law to address system chattering, achieving a control effect with no overshoot or chattering. The control method of the present invention can significantly reduce the phase lag of the brushless DC motor and increase its bandwidth. Furthermore, the method has numerous advantages, including simple structure, convenient calculation, and ease of implementation.

Description

Technical Field

[0001] The present invention relates to a BLDCM control system based on a novel approach rate sliding mode variable structure control, belonging to the technical field of BLDCM high-precision position control. Background Art

[0002] Brushless DC motors (BLDCs) offer advantages such as low failure rate, high efficiency, compact size, strong overload capacity, and simple drive control. They are widely used in robotics, CNC machine tools, and aerospace. Common control algorithms include PID control, adaptive control, and sliding mode variable structure control. BLDCMs are nonlinear and strongly coupled systems, making classical control theory inadequate for practical applications. Therefore, appropriate modern intelligent control algorithms are required.

[0003] For the control algorithms of BLDCM, the existing methods can be divided into two categories: one is the traditional control algorithm, which is convenient for engineering implementation, but this type of algorithm requires a model of the controlled object and has difficulty in dealing with the integral saturation problem when the error changes suddenly. It is usually used in systems with low performance requirements; the other is the intelligent control algorithm, including fuzzy control, optimization control, robust control, sliding mode control, neural network control, nonlinear control, adaptive control, etc. This type of control algorithm can be used for nonlinear systems, has high accuracy and good robustness, and is suitable for design and use in specific complex control objects. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and provide a BLDCM control system based on a new approach rate sliding mode variable structure control. The present invention adopts a new approach rate on the basis of traditional sliding mode variable structure control to achieve the requirements of reducing system overshoot, reducing phase lag, improving system bandwidth and solving system chattering problems. The method is simple to calculate and easy to implement, can be applied to different models of brushless DC motors, and has universality.

[0005] The technical solution of the present invention is:

[0006] The present invention discloses a BLDCM control system based on a novel reaching rate sliding mode variable structure control, comprising: a sliding mode variable structure controller, a PWM modulation unit, an inverter unit, a brushless DC motor and a position sensor unit; wherein the position sensor unit collects a motor position signal and transmits a motor angle signal to the sliding mode variable structure controller; the sliding mode variable structure controller adopts a sliding mode variable structure control method with a novel reaching law according to the motor position signal and an externally input reference position signal, and outputs a corresponding control signal to the PWM modulation unit; after receiving the control signal input by the sliding mode variable structure controller, the PWM modulation unit modulates and outputs a PWM control signal and a DIR control signal to the inverter unit; the inverter unit processes the PWM control signal and the DIR control signal and then drives the brushless DC motor to rotate to a specified position.

[0007] In the above control methods, the sliding mode variable structure control method of the new reaching law is specifically as follows:

[0008] Step S1, constructing a dynamic model of a brushless DC motor;

[0009] Step S2: establishing a system state equation according to the dynamic model;

[0010] Step S3, obtaining a hyperplane model of the system according to the system state equation;

[0011] Step S4, obtaining a sliding mode region model according to the hyperplane model;

[0012] Step S5: Obtaining the reaching law equation of the system according to the system state equation and the hyperplane model;

[0013] Step S6: Optimizing the reaching law equation to obtain a new reaching law formula with self-tuning capability;

[0014] Step S7: Obtain the sliding mode variable structure control rate of the entire sliding mode motion according to the new reaching law formula.

[0015] In the above control method, the sliding mode variable structure control rate in step S7 is expressed as follows:

[0016]

[0017] Among them, u is the sliding mode variable structure control rate; A, B, C are system parameters, J is the motor's moment of inertia, n e is the rated speed of the motor, x is the system state variable, γ is the external disturbance.

[0018] In the above control method, the dynamic model of the brushless DC motor in step S1 is specifically:

[0019]

[0020] Where: J is the motor's moment of inertia, is the friction torque, F e is the electromagnetic torque of the motor, p e is the electromagnetic power of the motor, n is the motor speed, is the angular velocity, is the rate of change of angular velocity.

[0021] In the above control method, the system state equation is established according to the dynamic model in step S2, specifically:

[0022]

[0023] in, is the system state variable, u is the system control variable, A and B are system parameters, γ is the external disturbance, Δθ is the angle deviation, is the rate of change of the angle deviation.

[0024] In the above control method, the hyperplane model of the system is obtained according to the system state equation in step S3, specifically:

[0025] s(x)=Cx=c1x1+c2x2+…+c n-1 x n-1 +…x n

[0026] Where C is the sliding mode parameter matrix, C=[c1,c2,…,c n-1 ,1];c1,c2,…,c n-1 are the n-1 parameters of the sliding mode, x1…x n is an n-dimensional state variable.

[0027] In the above control method, the sliding mode region model is obtained according to the hyperplane model in step S4, specifically:

[0028]

[0029] Where c1 is the sliding mode parameter, Δθ is the angle deviation, is the rate of change of the angle deviation.

[0030] In the above control method, the reaching law equation of the system is obtained according to the system state equation and the hyperplane model in step S5, which is specifically:

[0031]

[0032] in, is the reaching law, A, B, C are system parameters, x is the system state variable, u is the system control variable, and γ is the external disturbance.

[0033] In the above control method, the reaching law equation is optimized in step S6 to obtain a new reaching law formula with self-tuning capability, specifically:

[0034]

[0035] in, is a new reaching law, s is the sliding surface, exist Continuous.

[0036] In the above control method, the inverter unit is a low-voltage, high-current system, and the power switch tube adopts MOSFET, which has a current limiting function.

[0037] In the above control method, the inverter unit controls the speed of the brushless DC motor according to the PWM control signal, and controls the direction of the brushless DC motor according to the DIR control signal.

[0038] The beneficial effects of the present invention compared with the prior art are:

[0039] (1) The sliding mode zone coefficient of the present invention can be adjusted accordingly according to the rated speed of different types of motors, and has strong applicability.

[0040] (2) The present invention adopts a new approach rate and realizes parameter self-tuning based on the current state of the motor, and can adjust the approach rate according to the current state.

[0041] (3) The most important thing about this invention is that the new reaching law can effectively solve the problem of the traditional reaching law. The system chattering problem caused by discontinuous switching characteristics is solved to achieve a control effect with no overshoot and no chattering, significantly reducing the phase lag of the brushless DC motor and improving the system bandwidth.

[0042] (4) The present invention has a simple structure, is convenient to calculate, and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the overall block diagram of the BLDCM control system of the present invention.

[0044] Figure 2 It is the BLDCM driving principle diagram of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0046] The present invention discloses a BLDCM control system based on a novel reaching rate sliding mode variable structure control. The control system comprises a sliding mode variable structure controller, a PWM modulation unit, an inverter unit, a brushless DC motor, and a position sensor unit. The position sensor unit collects the motor position signal and transmits the motor angle signal to the sliding mode variable structure controller. The sliding mode variable structure controller uses a sliding mode variable structure control method with a novel reaching law based on the motor position signal and an externally input reference position signal to output a corresponding control signal to the PWM modulation unit. After receiving the control signal input from the sliding mode variable structure controller, the PWM modulation unit modulates and outputs a PWM control signal and a DIR control signal to the inverter unit. The inverter unit processes the PWM control signal and the DIR control signal and then drives the brushless DC motor to rotate to a specified position. The inverter unit is a low-voltage, high-current system, and its power switch tube uses a MOSFET with current limiting function. The inverter unit controls the speed of the brushless DC motor according to the PWM control signal and controls the direction of the brushless DC motor according to the DIR control signal.

[0047] The sliding mode variable structure control method based on the new reaching law is as follows:

[0048] Step S1, constructing a dynamic model of a brushless DC motor;

[0049] Step S2: establishing a system state equation according to the dynamic model;

[0050] Step S3, obtaining a hyperplane model of the system according to the system state equation;

[0051] Step S4, obtaining a sliding mode region model according to the hyperplane model;

[0052] Step S5: Obtaining the reaching law equation of the system according to the system state equation and the hyperplane model;

[0053] Step S6: Optimizing the reaching law equation to obtain a new reaching law formula with self-tuning capability;

[0054] Step S7: Obtain the sliding mode variable structure control rate of the entire sliding mode motion according to the new reaching law formula. The sliding mode variable structure control rate is:

[0055]

[0056] Among them, u is the sliding mode variable structure control rate; A, B, C are system parameters, J is the motor's moment of inertia, n e is the rated speed of the motor, x is the system state variable, γ is the external disturbance.

[0057] In step S1, the dynamic model of the brushless DC motor is specifically:

[0058]

[0059] Where: J is the motor's moment of inertia, is the friction torque, F e is the electromagnetic torque of the motor, p e is the electromagnetic power of the motor, n is the motor speed, is the angular velocity, is the rate of change of angular velocity.

[0060] In step S2, the system state equation is established according to the dynamic model, specifically:

[0061]

[0062] in, is the system state variable, u is the system control variable, A and B are system parameters, γ is the external disturbance, Δθ is the angle deviation, is the rate of change of the angle deviation.

[0063] In step S3, a hyperplane model of the system is obtained according to the system state equation, specifically:

[0064] s(x)=Cx=c1x1+c2x2+…+c n-1 x n-1 +…x n

[0065] Where C is the sliding mode parameter matrix, C=[c1,c2,…,c n-1 ,1];c1,c2,…,c n-1 are the n-1 parameters of the sliding mode, x1…x n is an n-dimensional state variable.

[0066] In step S4, the sliding mode region model is obtained according to the hyperplane model, specifically:

[0067]

[0068] Where c1 is the sliding mode parameter, Δθ is the angle deviation, is the rate of change of the angle deviation.

[0069] In step S5, the reaching law equation of the system is obtained according to the system state equation and the hyperplane model, specifically:

[0070]

[0071] in, is the reaching law, A, B, C are system parameters, x is the system state variable, u is the system control variable, and γ is the external disturbance.

[0072] In step S6, the reaching law equation is optimized to obtain a new reaching law formula with self-tuning capability, specifically:

[0073]

[0074] in, is a new reaching law, s is the sliding surface, exist Continuous.

[0075] Example

[0076] like Figure 1 As shown, the present invention proposes a BLDCM control system based on a new reaching rate sliding mode variable structure control, the control system includes a sliding mode variable structure controller, an inverter unit, a brushless DC motor and a position sensor unit; wherein the position sensor unit collects the motor angle signal and transmits the signal to the controller, the controller outputs a corresponding control signal through the input and output angle position signal and the sliding mode variable structure control algorithm of the new reaching law, after receiving the control quantity, the PWM modulation unit modulates and outputs two control signals PWM and DIR to the inverter unit, the PWM signal controls the speed, and the DIR signal controls the direction, the inverter unit has a power supply voltage of 28V and a maximum current of 10A, the power inverter circuit of this system is a low-voltage and high-current system, the power switch tube adopts MOSFET, and the circuit has a current limiting function; after the PWM signal is processed by the inverter circuit, it drives the brushless DC motor to rotate to the specified position.

[0077] The brushless DC motor position control system consists of five parts: sliding mode variable structure controller, PWM modulation unit, inverter unit, brushless DC motor and position sensor unit. The specific circuit structure and connection relationship of each part are described as follows.

[0078] The controller unit receives the control instruction, collects the position feedback signal of the position sensor through the AD acquisition circuit, calculates the corresponding control quantity through the sliding mode variable structure control algorithm with a new reaching law, and outputs PWM and DIR control signals through the PWM modulation unit. The PWM signal controls the speed and the DIR signal controls the direction. After the signal is processed by the inverter circuit, it drives the brushless DC motor to rotate to the specified position.

[0079] The input signal of the new reaching law sliding mode variable structure control is the command angle signal θ ref and the angle feedback signal θ collected by the position sensor fb , from which the angle deviation signal can be obtained as: Δθ=θ ref -θ fb.

[0080] The dynamic model of the brushless DC motor is:

[0081]

[0082] Where: J is the motor's moment of inertia, is the friction torque, F e is the electromagnetic torque of the motor, and p e is the electromagnetic power of the motor, and n is the motor speed.

[0083] Establish the state equation according to the kinetic model:

[0084]

[0085] in is the system state variable, u is the system control variable, A and B are system parameters, which can be determined according to the dynamic model γ is the external disturbance.

[0086] The control algorithm of this embodiment adopts sliding mode variable structure control. In the state space of the above system, there is a sliding mode surface s(x)=0. The sliding mode surface is the sliding mode region. The system performs sliding mode motion in the sliding mode region and continuously approaches s(0).

[0087] According to the system state equation (2), two hyperplanes are designed:

[0088] s(x)=Cx=c1x1+x2 (3)

[0089] The coefficient C in this formula is [c1, 1].

[0090] The sliding mode region of this system is:

[0091]

[0092] Generally, the larger the coefficient c is, the faster the zeroing speed is. In this embodiment, the parameter c is adjusted according to the rated speed of the motor. where n e is the rated speed of the motor, that is

[0093] From formula (2) and formula (3), we can deduce:

[0094]

[0095] The movement of a point outside the sliding mode region of the system approaching the sliding mode region is called approaching motion. Representing the reaching law, in order to improve the quality of the reaching motion, it is necessary to design an excellent reaching law formula suitable for this system. Based on the common constant velocity reaching law, exponential reaching law, power reaching law formula and their advantages and disadvantages, in this embodiment, the new reaching law formula is:

[0096]

[0097] The reaching law can realize the self-tuning of the reaching speed. The reaching speed is That is, the system approaching speed changes with the change of the system state. The farther away from the sliding surface, the faster the approaching speed, and the closer to the sliding surface, the slower the approaching speed. The approaching law is Continuous at all places, which can effectively solve the traditional reaching law The discontinuous switching characteristics cause system chattering problems.

[0098] Therefore, the control rate of the entire sliding mode motion can be expressed by Obtain:

[0099]

[0100] The control quantity output by the new reaching law sliding mode variable structure controller is output through the PWM modulation module to output a PWM control signal including the PWM output duty cycle size and direction DIR.

[0101] The PWM control signal is processed by the inverter circuit to drive the switch tube channel. The driving principle diagram is as follows Figure 2 As shown, the control signals PWM and DIR are processed, and then the logic signal for turning on the power tube of the inverter circuit is output. Because the PWM signal output by the control circuit is a digital signal with a high frequency, but low voltage and current, and low driving capability, level conversion and optoelectronic isolation are required to solve the problems of potential mismatch and interference between signals. The BLDCM power drive circuit has 6 switch tubes AH, BH, CH, AL, BL, and CL. The conduction mode is 2-2 conduction mode. The conduction sequence is that the two switch tubes AH and CL are turned on initially, and then switched to the two switch tubes CL and BH. The subsequent turn-on sequence is BHAL, ALCH, CHBL, BLAH, and AHCL. There are 6 commutations in one cycle, and the switch conduction state is changed every 60° electrical angle. Each switch tube is turned on for 120°, driving the brushless DC motor to receive the processed voltage signal and rotate to the specified position.

[0102] The above description is only the best specific implementation of the present invention, but the scope of protection of the present invention is not limited thereto. The contents not described in detail in the specification of the present invention belong to the common knowledge of professional and technical personnel in this field.

Claims

1. A BLDCM control system based on a new approach rate sliding mode variable structure control, characterized in that: include: A sliding mode variable structure controller, a PWM modulation unit, an inverter unit, a brushless DC motor, and a position sensor unit; wherein the position sensor unit collects the motor position signal and transmits the motor angle signal to the sliding mode variable structure controller; the sliding mode variable structure controller adopts a sliding mode variable structure control method with a novel reaching law based on the motor position signal and an externally input reference position signal, and outputs a corresponding control signal to the PWM modulation unit; after receiving the control signal input by the sliding mode variable structure controller, the PWM modulation unit modulates and outputs a PWM control signal and a DIR control signal to the inverter unit; the inverter unit processes the PWM control signal and the DIR control signal and then drives the brushless DC motor to rotate to a specified position; The sliding mode variable structure control method of the novel reaching law is specifically as follows: Construct a dynamic model of a brushless DC motor; Establish the system state equation according to the dynamic model; Obtaining a hyperplane model of the system according to the system state equation; The sliding mode region model is obtained based on the hyperplane model; According to the system state equation and hyperplane model, the reaching law equation of the system is obtained; The reaching law equation is optimized to obtain a new reaching law formula with self-tuning capability; The sliding mode variable structure control rate of the entire sliding mode motion is obtained according to the new reaching law formula; The reaching law equation is optimized to obtain a new reaching law formula with self-tuning capability, specifically: in, is a new reaching law, s is the sliding surface, exist Continuous.

2. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The sliding mode variable structure control rate is formulated as follows: Among them, u is the sliding mode variable structure control rate; A, B, C are system parameters, J is the motor's moment of inertia, n e is the rated speed of the motor, x is the system state variable, γ is the external disturbance.

3. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The dynamic model of the brushless DC motor is specifically: Where: J is the motor's moment of inertia, is the friction torque, F e is the electromagnetic torque of the motor, p e is the electromagnetic power of the motor, n is the motor speed, is the angular velocity, is the rate of change of angular velocity.

4. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The system state equation is established according to the dynamic model, specifically: in, is the system state variable, u is the system control variable, A and B are system parameters, γ is the external disturbance, Δθ is the angle deviation, is the rate of change of the angle deviation.

5. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1 is characterized in that: The hyperplane model of the system is obtained according to the system state equation, specifically: s(x)=Cx=c1x1+c2x2+…+c n-1 x n-1 +…x n Where C is the sliding mode parameter matrix, C=[c1,c2,…,c n-1 ,1];c1,c2,…,c n-1 are the n-1 parameters of the sliding mode, x1…x n is an n-dimensional state variable.

6. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The sliding mode region model is obtained according to the hyperplane model, specifically: Where c1 is the sliding mode parameter, Δθ is the angle deviation, is the rate of change of the angle deviation.

7. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The reaching law equation of the system is obtained according to the system state equation and the hyperplane model, specifically: in, is the reaching law, A, B, C are system parameters, x is the system state variable, u is the system control variable, and γ is the external disturbance.

8. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The inverter unit is a low-voltage, high-current system, and the power switch tube adopts MOSFET, which has a current limiting function.

9. The BLDCM control system based on the novel approach rate sliding mode variable structure control according to claim 1, characterized in that: The inverter unit controls the speed of the brushless DC motor according to the PWM control signal and controls the direction of the brushless DC motor according to the DIR control signal.

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