Sensorless control method for switched reluctance motor
By improving the sliding mode observer and using a novel approach law, the chattering problem of switched reluctance motors in harsh environments has been solved, achieving more stable sensorless control suitable for various working conditions.
Patent Information
- Application Number
- CN202510943385.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-09
- Publication Date
- 2025-10-31
AI Technical Summary
Traditional switched reluctance motors suffer from chattering issues when using position sensors in harsh environments, which affects system performance.
An improved sigmoid function is used to replace the sign function in the sliding mode observer, and a novel reaching law is designed to adjust the velocities of λ1 and λ2 to control the boundary layer. The switching state is optimized by combining the torque distribution function and the model predictive control strategy.
It effectively reduces system chattering under various operating conditions, improves system stability and adaptability, and reduces chattering when system state variables reach the sliding surface.
Smart Images
Figure CN120880274A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of motor control technology, specifically relating to a sensorless control method for a switched reluctance motor. Background Technology
[0002] Switched reluctance motors rely on precise rotor position information for commutation. Traditional position sensors diminish their advantages in harsh environments. The sliding mode observer method is a method that obtains position and speed by estimating back electromotive force or flux linkage, and has excellent dynamic performance. However, the traditional sliding mode observer method uses a sign function, which inevitably leads to chattering problems, and chattering can degrade system performance. Summary of the Invention
[0003] This application provides a sensorless control method for a switched reluctance motor to solve or partially solve the problems mentioned in the background art.
[0004] This application provides a sensorless control method for a switched reluctance motor, comprising the following steps:
[0005] Design a sliding mode observer;
[0006] The improved sigmoid function G(s) is used instead of the sign function sgn(s) in the sliding mode observer, as follows:
[0007]
[0008] λ1 affects the speed at which the function approaches 1. The larger λ1 is, the faster G(s) approaches 1, and the smaller the corresponding boundary layer. λ2 affects the speed at which the function approaches the origin. The larger λ2 is, the slower G(s) approaches the origin. Adjusting λ1 and λ2 can regulate the speed when approaching 1 and the origin. λ1 and λ2 are adjustment coefficients, and s is the sliding surface.
[0009] Preferably, a novel sliding mode reaching law is designed:
[0010]
[0011] In the formula, a function f(s) is introduced into the constant velocity reaching term, -ks is the exponential reaching term, the improved sigmoid function G(s) is used to replace the sign function sgn(s) in the sliding mode observer, and γ1, γ2 and γ3 are reaching law coefficients and are all greater than 0.
[0012] When the system state variable is far from the sliding surface, i.e., |s|→∞, the coefficient of the constant velocity approaching term approaches ε>1. Compared with the original exponential approaching law, the convergence speed is faster. When the system state variable is close to the sliding surface, i.e., |s|→0, the coefficient of the constant velocity approaching term approaches 0. This means that when the system trajectory approaches the sliding surface, the approaching speed will decrease and gradually approach 0. When the system state variable is far from the sliding surface, the approaching speed is greater than the constant velocity approaching rate.
[0013] Define the sliding surface as:
[0014]
[0015] Differentiating with respect to the sliding surface, we get:
[0016]
[0017] In the formula, θ and ω are the rotor position angle and angular velocity, respectively, and k ω1 k ω2 With k θ For the switching gain, e f To indirectly reflect e θ and e ω The error function, e θ e represents the rotation angle error. ω This refers to the angular velocity error.
[0018] When k θ >|e ω |,k ω1 ,k ω2 When >0, the disturbance term is ignored. k ω2 The larger value should be k. ω2 ≥10max(T L ) / J, D, J, T e T L These are the coefficient of friction, moment of inertia, electromagnetic torque, and load torque, respectively.
[0019] The state equation of the sliding mode observer can then be designed as follows:
[0020]
[0021] Preferably, after obtaining the rotational speed, a reference torque is generated by a speed controller (PI) and fed into the torque loop. The torque loop employs a composite control strategy of TSF and MPC. The TSF controls the total torque T. eref The phase reference torque T is distributed to each phase. pref And compared with the torque value T predicted by the torque calculation module at the next moment. p(k+1) is fed into the cost function of MPC. Based on the minimization of the cost function, the switching state under the optimal voltage vector is determined and given to the power converter to control the operation of SRM.
[0022] Preferably, based on the mathematical model of the switched reluctance motor (SRM), the forward Euler method is used to discretize the SRM mathematical model within one sampling period to obtain its prediction model as follows:
[0023]
[0024] In the formula, T s To control the period, θ(k+1), i(k+1), T p (k+1) and T e (k+1) represents the rotor position angle, current, p-phase torque, and total electromagnetic torque at time k+1, respectively. dsat L q A and B are the parameters of the flux linkage model of the switched reluctance motor.
[0025] Preferably, TSF will T eref The phase reference torque T is distributed to each phase. pref At that time, a cosine-type torque distribution function is used, as follows:
[0026]
[0027] In the formula, θ on Let θ be the opening angle. off For the shut-off angle, θ ov This is the reversal overlap angle.
[0028] Preferably, the cost function of MPC is:
[0029]
[0030] Compared with the prior art, the beneficial effects of this application are as follows:
[0031] This application uses an improved sigmoid function instead of the traditional sign function, making the boundary layer variable and thus reducing chattering, making it suitable for adjustment under various operating conditions. Furthermore, a novel reaching law is proposed, characterized by a proximity rate that varies with the sliding mode position. This reduces the time required for the system state variables to reach the sliding surface and effectively reduces chattering when the system state variables reach the sliding surface. Attached Figure Description
[0032] The present application will be further described below with reference to the accompanying drawings and embodiments.
[0033] Figure 1 This is a control structure diagram for a switched reluctance motor.
[0034] Figure 2 This is a schematic diagram of the novel reaching law sliding mode observer of this application.
[0035] Figure 3 This describes the variation of G(s) with different values of λ1.
[0036] Figure 4 This describes the variation of G(s) with different values of λ2. Detailed Implementation
[0037] The specification and claims use certain terms to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.
[0038] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0040] Example 1
[0041] like Figures 1 to 4 As shown, this application provides a sensorless control method for a switched reluctance motor, comprising the following steps:
[0042] Design a sliding mode observer;
[0043] The improved sigmoid function G(s) is used instead of the sign function sgn(s) in the sliding mode observer, as follows:
[0044]
[0045] λ1 affects the speed at which the function approaches 1. The larger λ1 is, the faster G(s) approaches 1, and the smaller the corresponding boundary layer. λ2 affects the speed at which the function approaches the origin. The larger λ2 is, the slower G(s) approaches the origin. Adjusting λ1 and λ2 can regulate the speed when approaching 1 and the origin. λ1 and λ2 are adjustment coefficients, and s is the sliding surface.
[0046] Specifically, based on the mathematical model of the switched reluctance motor, including the voltage equation, flux linkage equation, and torque equation, a sliding mode observer is designed. The mathematical model of the switched reluctance motor can be expressed as:
[0047]
[0048] In the formula, U p i p R and ψ p These represent the voltage, current, resistance, and flux linkage of the stator phase windings, respectively; θ and ω represent the rotor position angle and angular velocity, respectively; and T represents the rotor position angle and angular velocity, respectively. p For single-phase torque, D, J, Te, and TL are the friction coefficient, moment of inertia, electromagnetic torque, and load torque, respectively.
[0049] Based on the mathematical model of the switched reluctance motor, the traditional sliding mode observer state equation is designed as follows:
[0050]
[0051] In equation (2), k ω With k θ To switch the gain, e f To indirectly reflect e θ and e ω The error function.
[0052] Define the sliding surface as:
[0053]
[0054] The traditional exponential reaching law of the sliding mode observer is expressed as:
[0055]
[0056] In the formula, -εsgn(s) is the constant velocity approaching term and -ks is the exponential term. Using the constant velocity approaching law as the approaching law for velocity observation results in a slow convergence speed. Furthermore, using the sign function as the switching function inevitably leads to chattering problems.
[0057] Using an improved sigmoid function G(s) instead of the traditional sign function makes the boundary layer variable, thereby reducing chattering and making it suitable for regulation under various operating conditions. To reduce system chattering, the state linear feedback control region can be expanded by increasing the boundary layer thickness. In addition, with the same boundary layer, when the function is closer to the origin and the slope is smaller, the regulation amount of G(s) is more stable when performing continuous switching within the boundary layer. By adjusting λ1 and λ2, the speed when approaching 1 and the origin can be adjusted, thus making it suitable for regulation under various operating conditions.
[0058] To further reduce chattering, a novel sliding mode reaching law is designed:
[0059]
[0060] In the formula, the function f(s) is introduced into the constant velocity reaching term, which can effectively reduce the chattering of the system in the sliding mode. -ks is the exponential reaching term. The improved sigmoid function G(s) is used to replace the sign function sgn(s) in the sliding mode observer to further reduce steady-state chattering. γ1, γ2 and γ3 are reaching law coefficients and are all greater than 0.
[0061] When the system state variable is far from the sliding surface, i.e., |s|→∞, the coefficient of the constant velocity approaching term approaches ε>1. Compared with the original exponential approaching law, the convergence speed is faster. When the system state variable is close to the sliding surface, i.e., |s|→0, the coefficient of the constant velocity approaching term approaches 0. This means that when the system trajectory approaches the sliding surface, the approaching speed will decrease and gradually approach 0. When the system state variable is far from the sliding surface, the approaching speed is greater than the constant velocity approaching rate.
[0062] The characteristic of this new sliding mode approach rate is that the approach rate changes with the position of the sliding mode. This not only reduces the time required for the system state variables to reach the sliding surface, but also effectively reduces chattering when the system state variables reach the sliding surface.
[0063] Differentiating with respect to the sliding surface, we get:
[0064]
[0065] In the formula, θ and ω are the rotor position angle and angular velocity, respectively, and k ω1 k ω2 With k θ For the switching gain, e θ e represents the rotation angle error. ω For angular velocity error, e f To indirectly reflect e θ and e ω The error function.
[0066] When k θ >|e ω |,kω1 ,k ω2 When >0, the disturbance term is ignored. k ω2 The larger value should be k. ω2 ≥10max(T L ) / J, D, J, T e T L These are the coefficient of friction, moment of inertia, electromagnetic torque, and load torque, respectively.
[0067] The state equation of the sliding mode observer can then be designed as follows:
[0068]
[0069] e f To indirectly reflect e θ and e ω The error function, whose trend is similar to e ω Consistent, take e ω =ce f c > 0.
[0070] To prove the reachability of the reaching law, we choose the Lyapunov function:
[0071]
[0072] Differentiating the above equation, we get:
[0073]
[0074] Because c,k ω1 ,k ω2 >0, therefore Therefore, the designed reaching law satisfies the reachability condition, and the system tends to a stable state.
[0075] After obtaining the rotational speed, a reference torque is generated via a PI controller and fed into the torque loop. The torque loop employs a composite control strategy combining Torque Sharing Function (TSF) and Model Predictive Control (MPC). The TSF will control the total torque T... eref The phase reference torque T is distributed to each phase. pref And compared with the torque value T predicted by the torque calculation module at the next moment. p (k+1) is fed into the cost function of MPC. Based on the minimization of the cost function, the switching state under the optimal voltage vector is determined and given to the power converter to control the operation of SRM.
[0076] Based on the mathematical model of the switched reluctance motor (SRM), the forward Euler method is used to discretize the SRM mathematical model within one sampling period, resulting in the following prediction model:
[0077]
[0078] In the formula, T s To control the period, θ(k+1), i(k+1), T p (k+1) and T e (k+1) represents the rotor position angle, current, p-phase torque, and total electromagnetic torque at time k+1, respectively. dsat L q A and B are the parameters of the flux linkage model of the switched reluctance motor.
[0079] TSF will T eref The phase reference torque T is distributed to each phase. pref At that time, a cosine-type torque distribution function is used, as follows:
[0080]
[0081] In the formula, θ on Let θ be the opening angle. off For the shut-off angle, θ ov This is the reversal overlap angle.
[0082] In the SRM power converter, each phase has three operating states, represented as 1 (both upper and lower switches are turned on), 0 (one upper and lower switch is turned on and the other is turned off), and -1 (both upper and lower switches are turned off simultaneously). If only one prediction is performed, there are 27 possible combinations. To reduce the computational load of MPC, the voltage vector is determined by judging the relationship between the rotor position angle of each phase and the turn-on angle, turn-off angle, and commutation overlap angle of the SRM.
[0083] Taking phase A as an example, if θ A In θ on ~θ off +θ ov Within the specified range, the A-phase switch has two operating modes: 1 and 0. This is determined by comparing the voltage vectors T under the corresponding voltage vectors of 1 and 0. p (k+1), select the voltage vector with the minimum cost function for output; if θ A Not in θ on ~θ off +θ ov Within the range, the operating mode of phase A switch is -1.
[0084] The cost function of MPC is:
[0085]
[0086] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.
Claims
1. A sensorless control method for a switched reluctance motor, characterized in that, Includes the following steps: Design a sliding mode observer; The improved sigmoid function G(s) is used instead of the sign function sgn(s) in the sliding mode observer, as follows: λ1 affects the speed at which the function approaches 1. The larger λ1 is, the faster G(s) approaches 1, and the smaller the corresponding boundary layer. λ2 affects the speed at which the function approaches the origin. The larger λ2 is, the slower G(s) approaches the origin. Adjusting λ1 and λ2 can regulate the speed when approaching 1 and the origin. λ1 and λ2 are adjustment coefficients, and s is the sliding surface.
2. The sensorless control method for a switched reluctance motor according to claim 1, characterized in that: Design a novel sliding mode convergence law: In the formula, a function f(s) is introduced into the constant velocity reaching term, -ks is the exponential reaching term, the improved sigmoid function G(s) is used to replace the sign function sgn(s) in the sliding mode observer, and γ1, γ2 and γ3 are reaching law coefficients and are all greater than 0. When the system state variable is far from the sliding surface, i.e., |s|→∞, the coefficient of the constant velocity approaching term approaches ε>1. Compared with the original exponential approaching law, the convergence speed is faster. When the system state variable is close to the sliding surface, i.e., |s|→0, the coefficient of the constant velocity approaching term approaches 0. This means that when the system trajectory approaches the sliding surface, the approaching speed will decrease and gradually approach 0. When the system state variable is far from the sliding surface, the approaching speed is greater than the constant velocity approaching rate.
3. The sensorless control method for a switched reluctance motor according to claim 2, characterized in that: Define the sliding surface as: Differentiating with respect to the sliding surface, we get: In the formula, θ and ω are the rotor position angle and angular velocity, respectively, and k ω1 k ω2 With k θ For the switching gain, e f To indirectly reflect e θ and e ω The error function, e θ e represents the rotation angle error. ω This refers to the angular velocity error. When k θ >|e ω |,k ω1 ,k ω2 When >0, the disturbance term is ignored. k ω2 The value is k ω2 ≥10max(T L ) / J, D, J, T e T L These are the coefficient of friction, moment of inertia, electromagnetic torque, and load torque, respectively. The state equation of the sliding mode observer can then be designed as follows:
4. A sensorless control method for a switched reluctance motor according to any one of claims 1-3, characterized in that: After obtaining the rotational speed, a reference torque is generated via a PI controller and fed into the torque loop. The torque loop employs a combined control strategy of TSF and MPC. The TSF controls the total torque T... eref The phase reference torque T is distributed to each phase. pref And compared with the torque value T predicted by the torque calculation module at the next moment. p (k+1) is fed into the cost function of MPC. Based on the minimization of the cost function, the switching state under the optimal voltage vector is determined and given to the power converter to control the operation of SRM.
5. The sensorless control method for a switched reluctance motor according to claim 4, characterized in that: Based on the mathematical model of the switched reluctance motor (SRM), the forward Euler method is used to discretize the SRM mathematical model within one sampling period, resulting in the following prediction model: In the formula, T s To control the period, θ(k+1), i(k+1), T p (k+1) and T e (k+1) represents the rotor position angle, current, p-phase torque, and total electromagnetic torque at time k+1, respectively. dsat L q A and B are the parameters of the flux linkage model of the switched reluctance motor.
6. The sensorless control method for a switched reluctance motor according to claim 4, characterized in that: TSF will T eref The phase reference torque T is distributed to each phase. pref At that time, a cosine-type torque distribution function is used, as follows: In the formula, θ on Let θ be the opening angle. off For the shut-off angle, θ ov This is the reversal overlap angle.
7. A sensorless control method for a switched reluctance motor according to claim 4, characterized in that: The cost function of MPC is: