A load and temperature constraint based stepping motor current reference optimization method

Abstract

The application discloses a stepping motor current given value optimization method based on load and temperature constraints and relates to the technical field of motor control.The application adopts a compound current given value strategy combining feedforward compensation with feedback compensation.The feedforward compensation link compensates for the inertia torque generated in the acceleration and deceleration process, effectively reducing the risk of step loss in the acceleration and deceleration stage; the feedback compensation link dynamically adjusts the driving current based on the shaft end output torque, so that the driving current accurately adapts to the needs of the real-time load. Meanwhile, a temperature-load current constraint mechanism with winding temperature and load rate as inputs is established, and threshold constraints are applied to the current given value through a two-dimensional lookup table. In addition, the feedforward compensation coefficient is adjusted online through a cycle-by-cycle recursive identification algorithm, realizing adaptive compensation for motor system parameter drift and load working condition changes. The application can significantly reduce the operating current and winding temperature rise of the motor, effectively improving the dynamic performance, operating efficiency and thermal management level of the motor system.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method for optimizing the current setting of a stepper motor based on load and temperature constraints. Background Technology

[0002] Stepper motors, with their advantages of high positioning accuracy, open-loop control, and high low-speed output torque, have been widely used in high-end equipment fields such as industrial automation, robotics, and aerospace. However, traditional stepper motor drive systems generally adopt a constant current chopper drive strategy, meaning that the motor is driven with a fixed current setpoint throughout its entire operating condition. When the motor is under light load or running at a constant speed, the actual torque required is less than the rated torque. Excessive drive current leads to a large amount of electrical energy being converted into heat energy loss, reducing the operating efficiency of the motor drive system and causing severe heating of the motor windings, accelerating the aging of the winding insulation layer, and thus shortening the overall service life of the stepper motor. To improve the energy consumption and temperature rise defects of traditional constant current drive schemes, various optimized drive schemes have been proposed in existing technologies. Among them, the load-adaptive current regulation method can dynamically adjust the drive current by detecting the motor load status, reducing the current to reduce losses under light load. However, this method only adjusts for steady-state loads and cannot effectively distinguish and compensate for the inertial torque during the dynamic operation of the motor during acceleration and deceleration. This can easily lead to insufficient current during acceleration, causing the motor to lose steps, and excessive current during constant speed, resulting in energy waste. Another current-limiting drive strategy based on temperature feedback forcibly reduces the drive current when the winding temperature exceeds the threshold. However, this passive protection method not only reduces the dynamic response performance of the motor system, but also cannot achieve fine-grained current optimization distribution according to actual temperature changes and real-time load requirements.

[0003] Furthermore, existing drive technologies also have shortcomings in parameter identification and adaptive control. Some solutions require pre-obtaining key parameters such as motor inertia through offline calibration, which is a cumbersome process. Once the obtained parameters are fixed, they cannot adapt to system parameter drift caused by external factors such as motor aging and changes in ambient temperature. The few optimization solutions that use online parameter identification rely heavily on complex algorithms such as state observers, which involve large computational loads and are difficult to implement in resource-constrained embedded control processors, thus lacking practicality.

[0004] In summary, existing stepper motor drive technologies suffer from numerous limitations, including incomplete energy consumption optimization, poor winding temperature rise control, suboptimal dynamic performance, and weak parameter self-adaptation capabilities. These limitations prevent the simultaneous fulfillment of practical application requirements such as stable and reliable motor operation, low power consumption, and low temperature rise. Therefore, there is an urgent need for a stepper motor current setting optimization method that can adapt to dynamic load changes while considering temperature constraints. This method should minimize power consumption and winding temperature rise while ensuring stable and reliable motor operation, thereby improving the overall operating efficiency of the stepper motor drive system. Summary of the Invention

[0005] In view of at least one of the above technical problems, this application provides a stepper motor current setting optimization method based on load and temperature constraints. By combining feedforward compensation and feedback compensation with composite dynamic current compensation and temperature-load current constraints, the method achieves adaptive optimization of stepper motor current setting. This effectively solves the problems of traditional stepper motor drive systems, such as passive current limiting leading to step loss, high energy consumption, rapid winding temperature rise, inability to perform fine current distribution according to actual temperature and load requirements, and complex automatic parameter identification and adaptive control processes. This significantly improves the dynamic performance, energy efficiency and thermal management level of the motor.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for optimizing the current setting of a stepper motor based on load and temperature constraints, the method comprising:

[0008] Each motion cycle of a stepper motor is defined as consisting of multiple control cycles, and each motion cycle includes an acceleration segment and a constant speed segment;

[0009] Obtain the stepper motor's shaft-end output torque, winding temperature, and target acceleration 'a' for each control cycle. target ;

[0010] The method also includes:

[0011] According to the preset operating current setpoint I run Drive the stepper motor into the initial operation phase and calculate the feedforward compensation coefficient k obtained from the first identification. a (1); From obtaining k a (1) The next control cycle after which the system enters the normal operation phase;

[0012] Based on the current feedforward compensation coefficient, the feedforward compensation coefficient is updated using a cycle-by-cycle recursive identification algorithm during normal operation.

[0013] In each control cycle during normal operation, the following steps are performed:

[0014] According to the current a target Calculate the feedforward compensation current I using the feedforward compensation coefficient. ff Calculate the feedback compensation current I based on the current shaft end output torque. fb and load factor η; based on I ff and I fb Calculate the current given preset value I preset ;

[0015] Based on the current winding temperature and η, the maximum current threshold I under the current operating condition is obtained by matching with the current temperature-load constraint table. limit ; take I preset with I limit The minimum of the two values ​​is used as the final current setpoint I for the current control cycle. final .

[0016] Furthermore, according to the aforementioned stepper motor current setting optimization method based on load and temperature constraints, the initial running phase is the identification window phase of the first motion cycle, that is, the running phase from the first start of the motor to the end of the identification window of the first motion cycle; the identification window phase consists of all acceleration segments and the first N constant speed segments within the motion cycle. c The control cycle consists of several cycles; within the identification window phase of each motion cycle, the feedforward compensation coefficient k is adjusted. a Online identification is performed, and the identification results take effect immediately for the remainder of the current motion cycle, and are used to calculate the feedforward compensation current.

[0017] Furthermore, according to the aforementioned method for optimizing stepper motor current feedforward based on load and temperature constraints, the calculation of the feedforward compensation coefficient k obtained from the initial identification... a (1), including:

[0018] Step 2.1: Calculate the average shaft-end output torque during the acceleration phase in the initial operation stage. and the average shaft end output torque during the constant speed segment ;

[0019] The shaft-end output torque sequence of all control cycles during the acceleration phase in the initial operation stage is collected, and then the average shaft-end output torque during the acceleration phase in the initial operation stage is calculated. ; Collect data during the initial uniform speed phase, N c The shaft-end output torque sequence of each control cycle is used to calculate the average shaft-end output torque during the constant speed segment in the initial operation phase. ;

[0020] Step 2.2: Based on and The feedforward compensation coefficient k obtained from the first identification was calculated using the single-difference method. a (1) The specific calculation formula is as follows:

[0021] ;

[0022] Among them, K T a is the torque coefficient; target (1) is the target acceleration for the first motion cycle.

[0023] Furthermore, according to the aforementioned method for optimizing the current setting of a stepper motor based on load and temperature constraints, the step of updating the feedforward compensation coefficients using a cycle-by-cycle recursive identification algorithm during normal operation includes:

[0024] Step 6.1: In the acceleration phase of the current nth motion cycle, collect the shaft-end output torque sequence for all control cycles within the acceleration phase, and calculate the average shaft-end output torque of the acceleration phase. During the uniform velocity segment of the current nth motion cycle, collect the data from the first N segments of the uniform velocity segment. c The sequence of shaft-end output torque for each control cycle is calculated, and the average shaft-end output torque during the constant speed segment is also calculated. ;

[0025] Step 6.2: With the target acceleration a in the current motion cycle target (n) as a regression variable ,based on and The observed value y(n) for the current motion cycle is calculated using the following formula:

[0026] ;

[0027] Where n is the sequence number of the motion cycle; The average shaft-end output torque during the acceleration phase of the nth motion cycle; K represents the average shaft-end output torque during the uniform speed segment of the nth motion cycle. T a is the torque coefficient; target (n) represents the target acceleration in the nth motion cycle; For the nth motion cycle, it is the regression variable;

[0028] Step 6.3: Based on regression variables Calculate the recursive gain K for the current motion cycle. n (n), the latest feedforward compensation coefficient k is calculated based on the observation y(n). a (n) and based on the recursive gain K n (n) Update the current motion cycle The estimation error covariance P(n);

[0029] The regression variable Calculate the recursive gain K for the current motion cycle. n (n), specifically implemented through the following formula:

[0030] ;

[0031] Among them, K n (n) represents the recursive gain of the nth motion cycle, where n is the motion cycle number; P(n-1) represents the (n-1)th motion cycle. The estimation error covariance; λ is the forgetting factor;

[0032] The latest feedforward compensation coefficient k is calculated based on the observed value y(n). a (n), specifically implemented through the following formula:

[0033] ;

[0034] Among them, K n (n) represents the recursive gain for the nth motion cycle, where n ≥ 2; k a (n) is the feedforward compensation coefficient for the nth motion cycle; Let be the regression variable for the nth exercise cycle; y(n) be the observation for the nth exercise cycle; k a (n-1) represents the feedforward compensation coefficients obtained during the (n-1)th motion cycle.

[0035] The recursive gain K n (n) Update the current motion cycle The estimation error covariance P(n) is specifically achieved through the following formula:

[0036] ;

[0037] Where λ is the forgetting factor; P(n) is the k of the nth motion cycle. a The estimation error covariance of (n) is given by P(1), which is a preset positive number; K n (n) represents the recursive gain for the nth motion cycle; For the nth motion cycle, it is the regression variable; For the (n-1)th motion cycle The estimation error covariance.

[0038] Furthermore, according to the aforementioned stepper motor current setting optimization method based on load and temperature constraints, the stepper motor current setting optimization method based on the current a... target Calculate the feedforward compensation current I using the feedforward compensation coefficient. ff ,include:

[0039] Step 3.1: Based on the target acceleration a of the stepper motor target and the latest feedforward compensation coefficient k a Calculate the feedforward compensation current I ff Specifically, this is achieved through the following formula:

[0040] ;

[0041] Among them, I ff(k) represents the feedforward compensation current for the kth control cycle within the current motion cycle; a target (k) represents the target acceleration in the kth control cycle within the current motion cycle, K T The torque coefficient is used; before the end of the identification window phase of the nth motion cycle, the latest feedforward compensation coefficient is taken as the feedforward compensation coefficient k obtained from the identification of the previous motion cycle. a (n-1), after the nth motion cycle identification window phase ends, the latest feedforward compensation coefficient is taken as k obtained from the current motion cycle identification. a (n).

[0042] Furthermore, according to the aforementioned stepper motor current setting optimization method based on load and temperature constraints, the step of calculating the feedback compensation current I based on the current shaft-end output torque... fb and load factor η, including:

[0043] Step 3.2: Calculate the load rate change between adjacent control cycles within the current motion cycle. The specific calculation formula is as follows:

[0044] ;

[0045] in, For the current movement cycle, the first Load rate per control cycle; For the current movement cycle, the first Load rate per control cycle; For the current movement cycle, the first The first control cycle and the adjacent first The change in load rate between control cycles;

[0046] Step 3.3: Define a piecewise nonlinear mapping function based on the load factor η. The details are as follows:

[0047] ;

[0048] Where η1 and η2 are the load rate segmentation thresholds; k1, k2, and k3 are the gain coefficients; I run The initial operating current is preset, and I run Less than or equal to the rated current I rated ;

[0049] Step 3.4: Based on and Calculate the feedback compensation current I fb The specific calculation formula is as follows:

[0050] ;

[0051] Among them, I fb (k) represents the feedback compensation current for the kth control cycle within the current motion cycle; It is a piecewise nonlinear mapping function based on the load factor η, that is, a piecewise mapping component based on the load factor; This represents the change in load rate between two adjacent control cycles, the k-th control cycle and the (k-1)-th control cycle, within the current motion cycle; k d The differential gain coefficient; For the load rate-based differential feedforward component of the k-th control cycle within the current motion cycle; It is an advance compensation given after predicting the sudden change trend of load rate between adjacent control cycles, which is used to improve the dynamic response speed to load changes.

[0052] Furthermore, according to the aforementioned stepper motor current setting optimization method based on load and temperature constraints, the method based on I... ff and I fb Calculate the current given preset value I preset ,include:

[0053] Step 4.1: Adjust the feedforward compensation current I ff The slope rate of change speed limiting process is applied to obtain the processed feedforward compensation current. The feedforward compensation current change in each control cycle is limited to not exceeding the preset maximum current change rate ΔI. max Specifically, this is achieved through the following formula:

[0054] ;

[0055] Among them, I ff (k) is the feedforward compensation current for the kth control cycle within the current motion cycle; This is the feedforward compensation current output value after slope rate of change speed limiting processing in the kth control cycle within the current motion cycle; This is the feedforward compensation current output value after slope rate limiting processing in the (k-1)th control cycle within the current motion cycle.

[0056] Step 4.2: Adjust the feedback compensation current value I fb Perform a first-order low-pass filter to obtain the filtered feedback compensation current output value I. fb_filt Specifically, this is achieved through the following formula:

[0057] ;

[0058] Where α is the filter coefficient; I fb (k) represents the feedback compensation current for the k-th control cycle within the current motion cycle, I.fb_filt (k) represents the filtered feedback compensation current output value in the kth control cycle within the current motion cycle, I fb_filt (k-1) is the filtered feedback compensation current output value in the (k-1)th control cycle within the current motion cycle;

[0059] Step 4.3: Process the feedforward compensation current The processed feedback compensation current I fb_filt With the set value I of the holding current hold Summing yields the current preset value I for the current control cycle within the current motion cycle. preset .

[0060] Furthermore, according to the aforementioned stepper motor current setting optimization method based on load and temperature constraints, the current winding temperature and η are matched with the current temperature-load constraint table to obtain the maximum current threshold I under the current operating condition. limit ,include:

[0061] Step 5.1: Using the current winding temperature T and load rate η as lookup table indices, match them in the current temperature-load constraint table with a two-dimensional lookup table structure to obtain the corresponding current threshold coefficient. ;

[0062] Step 5.2: Based on the current threshold coefficient Calculate the maximum current threshold I of the current control cycle within the current motion cycle. limit The specific calculation formula is as follows:

[0063] ;

[0064] Among them, I rated This is the rated current of the motor; This represents the current threshold coefficient corresponding to the current winding temperature T and load rate η under the current winding temperature and load rate conditions, where T is the winding temperature and η is the load rate.

[0065] Furthermore, according to the aforementioned method for optimizing stepper motor current setting based on load and temperature constraints, the method further includes: an initial temperature-load constraint table is pre-configured manually; after the preset initial temperature-load constraint table is put into operation, the temperature-load constraint table supports online self-correction and updating, and the updating method specifically includes:

[0066] During motor operation, the winding temperature of the current control cycle within the current motion cycle is acquired, and the temperature rise rate dT / dt of the winding is calculated in real time; when the temperature rise rate of the winding exceeds the preset temperature rise rate threshold (dT / dt)... th At that time, for the current operating point Current threshold coefficient Perform a downward adjustment to obtain the corrected current threshold coefficient. Similarly, when the temperature rise rate is below the threshold, the current threshold coefficient can be increased, but the increased value will... The current threshold is adjusted bidirectionally and adaptively, ensuring it does not exceed the initial value of the operating point corresponding to the initial temperature-load constraint table. This is achieved through the following formula:

[0067] ;

[0068] in, Current operating point The corrected current threshold coefficient; dT / dt is the current operating point. The rate of temperature rise of the winding; (dT / dt) th Current operating point The preset winding temperature rise rate threshold; μ is the correction step size coefficient.

[0069] The beneficial effects of adopting the above technical solution are as follows:

[0070] (1) A composite current feedforward compensation and feedback compensation strategy is adopted to achieve accurate load compensation for the stepper motor under all operating conditions. Among them, the feedforward compensation stage compensates for the inertial torque generated during acceleration and deceleration, effectively reducing the risk of step loss during acceleration and deceleration; the feedback compensation stage dynamically adjusts the drive current based on the shaft-end output torque, so that the drive current under uniform speed and light load conditions is accurately adapted to the actual load requirements. This can significantly reduce the motor operating current, effectively suppress the winding temperature rise, and improve the efficiency of the motor system.

[0071] (2) A temperature-load current constraint mechanism is established with winding temperature and load rate as input variables. A two-dimensional lookup table representing the temperature-load current constraint relationship is used to apply threshold constraints to the current setpoint, while also having an online self-correction function. Compared with the traditional passive current limiting method with a single temperature threshold, this invention can limit the current in stages according to the real-time temperature and load status, effectively avoiding insulation aging problems caused by winding overheating, extending the service life of the motor, and significantly improving the intelligence level of thermal management and long-term operational reliability of the motor system.

[0072] (3) The feedforward compensation coefficient is tuned online using a cycle-by-cycle recursive identification method. This method can automatically identify parameters without the need for additional sensors or offline calibration, and can adaptively compensate for drift in motor system parameters and changes in load conditions. Only one recursive calculation is required in each motion cycle, resulting in a small computational load. It can run stably and in real time on resource-constrained embedded control processors, making it highly practical. Attached Figure Description

[0073] Figure 1An overall flowchart of a stepper motor current setting optimization method based on load and temperature constraints is provided in this embodiment of the invention;

[0074] Figure 2 This is a schematic diagram of the target speed curve of a stepper motor within one motion cycle, provided in an embodiment of the present invention.

[0075] Figure 3 This is a schematic diagram showing the details of the control cycle for a local uniform velocity segment within the motion cycle provided in an embodiment of the present invention;

[0076] Figure 4 This is a schematic diagram of a current-given curve during a motion cycle provided in an embodiment of the present invention;

[0077] Figure 5 A principle block diagram for optimizing the current setting of a stepper motor based on load and temperature constraints, provided in an embodiment of the present invention;

[0078] Figure 6 A flowchart for current calculation and output within a control cycle provided in an embodiment of the present invention;

[0079] Figure 7 This is a flowchart of online recursive identification of feedforward compensation coefficients within the identification window stage provided in an embodiment of the present invention;

[0080] Figure 8 A piecewise nonlinear mapping function curve based on load rate in feedback compensation provided in an embodiment of the present invention;

[0081] Figure 9 A flowchart illustrating the online self-correction of the temperature-load constraint table provided in an embodiment of the present invention. Detailed Implementation

[0082] To describe the present invention in more detail, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0083] In this embodiment, the invention relates to two different time scales: a control cycle and a motion cycle. A motion cycle consists of multiple control cycles. Taking the control cycle of the motor system as 0.5 ms and the motion cycle as 5 s, in this embodiment, one motion cycle contains 10,000 control cycles. Each complete motion cycle of the stepper motor includes at least an acceleration phase and a constant speed phase, and optionally a deceleration phase, such as... Figure 2 and Figure 3 As shown, T c This represents the time length of each control cycle within the uniform speed segment.

[0084] I runUnlike traditional methods that use a preset constant current, this invention can dynamically adjust the current based on the real-time load. In this embodiment, for example... Figure 4 As shown, the actual given current value compared to I run This reduces ΔI. The magnitude of ΔI is affected by the actual load rate η. The smaller the load rate η, i.e., the lighter the load, the larger ΔI will be, and the more significant the energy-saving effect will be.

[0085] The overall process of this invention is divided into two stages:

[0086] (1) Initial operation phase (step 2): The initial operation phase is the identification window phase of the first motion cycle, that is, the operation phase from the first start of the motor to the end of the identification window of the first motion cycle; the initial operation phase is executed only once to complete k a Initial value identification.

[0087] (2) Normal operation phase (steps 3-7): The normal operation phase is the entire operation phase from the end of the initial operation phase to the end of the next control cycle until the motor stops; the normal operation phase is executed repeatedly to complete the dynamic optimization of the current command; and in the identification window phase of the new motion cycle, k is adjusted. a Perform the recursive identification in step 6.

[0088] The identification window phase consists of all acceleration segments and the first N segments of constant velocity segments within the motion cycle. c It consists of N control cycles. c In this embodiment, a value of 200 (corresponding to a 100ms sampling window) is preferred. During the identification window phase within each motion cycle, the feedforward compensation coefficient k is adjusted. a Online identification is performed, and the identification results take effect immediately for the remainder of the current motion cycle, used to calculate the feedforward compensation current, such as... Figure 7 As shown.

[0089] In the initial operation phase, k is obtained using the single-difference method. a The accurate initial value allows the feedforward compensation current to be calculated during the uniform velocity segment of the first motion cycle, providing initial values ​​for the recursive least squares method. In subsequent motion cycles (n≥2), the recursive least squares method with a forgetting factor is used to calculate k. a Continuous recursive optimization overcomes the limitations of the single-difference method, such as weak noise resistance and inability to track time-varying parameters.

[0090] The stepper motor current setting optimization method based on load and temperature constraints, such as Figure 1 As shown, perform the following steps:

[0091] Step 1: After the stepper motor starts, the shaft-end output torque, winding temperature information, and target motion parameters of the stepper motor are collected during the control cycle of each motion cycle; the target motion parameters include at least the target acceleration a. target ;

[0092] After the stepper motor enters the nth (n≥1) motion cycle, the shaft-end output torque, winding temperature information, and target motion parameters of the stepper motor are collected in real time during each control cycle, such as... Figure 6 As shown;

[0093] In practical implementation, those skilled in the art can use any known technical means to obtain the shaft-end output torque. For example, it can be directly measured using torque sensors, strain gauges, etc., or obtained through sensorless methods such as load angle estimation and state observers. Similarly, those skilled in the art can use any known technical means to obtain winding temperature information. For example, it can be obtained through direct measurement using external temperature sensors, inverse estimation through winding resistance measurement, or estimation based on a motor thermal model.

[0094] In a preferred embodiment, the output torque at the shaft end of the stepper motor is obtained through a torque sensor, and the winding temperature information of the stepper motor is obtained through an external temperature sensor. Then, the target acceleration 'a' of the stepper motor is obtained. target The target motion parameters;

[0095] The shaft-end output torque is the actual mechanical torque output from the stepper motor shaft end, including the load torque required for the motor to drive the external load and the friction damping torque of the transmission link; the load is the total torque load that the stepper motor needs to overcome during operation, including the shaft-end output torque and the inertial torque generated during acceleration and deceleration to overcome the system inertia.

[0096] Step 2: Simultaneously with the start of the stepper motor, the initial running phase begins, operating at the preset current setpoint I. run Start the stepper motor drive; calculate the feedforward compensation coefficient k obtained from the initial identification. a (1); from completing k a (1) Starting from the next control cycle after identification, the normal operation phase begins;

[0097] This step is the initial operation phase and is executed only once during the identification window phase of the first motion cycle (n=1). After execution, the system enters the normal operation phase (steps 3-7), and this step will not be triggered again. Step 2 specifically includes the following steps:

[0098] Step 2.1: Calculate the average shaft-end output torque during the acceleration phase in the initial operation stage. and the average shaft end output torque during the constant speed segment ;

[0099] Since there is no k in this stage a The identification value is insufficient to calculate the feedforward compensation current; therefore, this stage operates based on the preset operating current setpoint I. run Driver, where I run The traditional stepper motor current control method uses a preset constant current, I run The value is related to the load and must be less than or equal to the rated current I. rated .

[0100] Simultaneously, the shaft-end output torque sequence of all control cycles during the acceleration phase in the initial operation stage is collected, and the average shaft-end output torque during the acceleration phase in the initial operation stage is calculated. ; Collect data during the initial uniform speed phase, N c The sequence of shaft-end output torque for each control cycle is calculated, and the average shaft-end output torque during the constant speed segment in the initial operation phase is also calculated. In this embodiment, N is preferred. c =200 (corresponding to a 100ms sampling window).

[0101] Step 2.2: Based on and Calculate the feedforward compensation coefficient k obtained from the first identification. a (1);

[0102] The k is calculated directly using the single-difference method. a Initial recognition value:

[0103] (1)

[0104] in, The average shaft-end output torque during the acceleration phase of the first motion cycle; The average shaft-end output torque during the uniform speed segment of the first motion cycle; K T The torque coefficient can be determined by the parameters of the selected stepper motor; a target (1) is the target acceleration for the first motion cycle; k a (1) is the feedforward compensation coefficient obtained in the first identification.

[0105] Step 2.3: From completing k a (1) Starting from the next control cycle after identification, the system enters the normal operation phase. Thereafter, all control cycles will perform current setting calculation and output according to the normal operation phase process.

[0106] k a (1) As the initial value of the subsequent recursive least squares method, the initial value P(1) of the estimation error covariance P in the recursive least squares method is preset to a large positive number. In this embodiment, P(1) = 1000 is preferred.

[0107] To avoid drive current from I run Switch directly to I final The generated current step impact, the N immediately following the end of the first motion cycle identification window trans The gradual transition mechanism is activated in each control cycle. During the gradual transition, the actual output current setpoint I... trans Calculated from step 5.5.

[0108] Step 3: During normal operation, within each motion cycle's control period, based on the current target acceleration a... target Calculate the feedforward compensation current I using the latest feedforward compensation coefficients. ff Calculate the feedback compensation current I based on the current shaft end output torque. fb and load rate ;

[0109] Starting from the next control cycle after the end of the first motion cycle identification window, the feedforward compensation current I is calculated in each control cycle as follows: ff and feedback compensation current I fb The principle block diagram for optimizing the current setpoint of a stepper motor based on load and temperature constraints is as follows: Figure 5 As shown.

[0110] Step 3 specifically includes the following steps:

[0111] Step 3.1: Based on the target acceleration a of the stepper motor target and the latest feedforward compensation coefficient k a Calculate the feedforward compensation current I ff ,Right now:

[0112] (2)

[0113] Among them, I ff (k) represents the feedforward compensation current for the kth control cycle within the current motion cycle; a target (k) represents the target acceleration in the k-th control cycle within the current motion cycle. Before the end of the identification window phase in the n-th motion cycle, the latest feedforward compensation coefficient is taken as the feedforward compensation coefficient k obtained from the identification in the previous motion cycle. a (n-1), after the nth motion cycle identification window phase ends, the latest feedforward compensation coefficient is taken as k obtained from the current motion cycle identification. a (n). The latest feedforward compensation coefficients are calculated in step 6.3.

[0114] Step 3.2: Calculate the load rate change between adjacent control cycles within the current motion cycle. The specific calculation formula is as follows:

[0115] (3)

[0116] in, For the current movement cycle, the first The load rate for each control cycle, the load rate It is derived from the shaft-end output torque and is the ratio of the shaft-end output torque to the rated output torque of the motor, with a value range of 0~100%. For the current movement cycle, the first Load rate per control cycle; For the current movement cycle, the first The first control cycle and the adjacent first The change in load rate between control cycles.

[0117] Step 3.3: Define a piecewise nonlinear mapping function based on the load factor η. ;

[0118] like Figure 8 As shown, the piecewise nonlinear mapping function based on the load factor η The definition of is:

[0119] (4)

[0120] Wherein, the load rate η is calculated from the shaft-end output torque, and its value ranges from 0 to 100%; η1 and η2 are the load rate segment thresholds, and in this embodiment, η1=30% and η2=70% are preferred; k1, k2, and k3 are gain coefficients, with typical values ​​of k1=0.3 to 0.5, k2=0.2 to 0.4, and k3=0.3 to 0.5; I run I is the preset initial operating current. run The value is related to the load and must be less than or equal to the rated current I. rated .

[0121] When 0≤η<η1, the motor is in the light load region, and the feedforward current plus the holding current is sufficient, so no additional compensation is needed to reduce energy consumption; when η1≤η<η2, the motor is in the medium load region, and the compensation current increases linearly with the increase of load; when η≥η2, the motor is in the heavy load region, and the load is close to the motor limit. A composite growth strategy of a first-order plus a second-order function is adopted to quickly increase the current command to ensure torque margin and prevent loss of synchronism.

[0122] Step 3.4: Based on and Calculate the feedback compensation current I fb ;

[0123] Feedback compensation current I fbIncluding piecewise mapped components and differential feedforward components based on load factor, the feedback compensation current I is calculated. fb The formula is:

[0124] (5)

[0125] Among them, I fb (k) represents the feedback compensation current for the kth control cycle within the current motion cycle; It is a piecewise nonlinear mapping function based on the load factor η, that is, a piecewise mapping component based on the load factor; This represents the change in load rate between two adjacent control cycles, the k-th control cycle and the (k-1)-th control cycle, within the current motion cycle; k d This is the differential gain coefficient, typically ranging from 0.1 to 0.3. This represents the load-rate-based differential feedforward component for the k-th control cycle within the current motion cycle. It is an advance compensation given after predicting the sudden change trend of load rate between adjacent control cycles, which is used to improve the dynamic response speed to load changes.

[0126] Step 4: During the control cycle of each motion cycle, based on the feedforward compensation current I ff and feedback compensation current I fb Calculate the current given preset value I preset ;

[0127] For feedforward compensation current I ff Implement slope rate of change speed limiting processing and adjust the feedback compensation current I. fb Perform low-pass filtering smoothing; then sum the processed feedforward compensation current, the processed feedback compensation current, and the setpoint of the holding current to obtain the current preset value. Specifically, this includes the following steps:

[0128] Step 4.1: Adjust the feedforward compensation current I ff Applying a slope rate of change speed limit, we obtain... ;

[0129] For feedforward compensation current I ff The slope rate of change speed limiting process is applied to obtain the processed feedforward compensation current. The feedforward compensation current change in each control cycle is limited to not exceeding the preset maximum current change rate ΔI. max Specifically, this is achieved through the following formula:

[0130] (6)

[0131] Among them, I ff (k) is the feedforward compensation current for the kth control cycle within the current motion cycle; This is the feedforward compensation current output value after slope rate of change speed limiting processing in the kth control cycle within the current motion cycle; The feedforward compensation current output value after slope rate limiting processing is the k-1th control cycle within the current motion cycle, calculated from the previous control cycle within the current motion cycle.

[0132] Step 4.2: Adjust the feedback compensation current value I fb Perform a first-order low-pass filter to obtain I fb_filt ;

[0133] A first-order filter is used to compensate the feedback current value I. fb Perform a first-order low-pass filter to obtain the filtered feedback compensation current output value I. fb_filt Specifically, this is achieved through the following formula:

[0134] (7)

[0135] Where α is the filter coefficient, typically ranging from 0.05 to 0.2; I fb (k) represents the feedback compensation current for the k-th control cycle within the current motion cycle, I. fb_filt (k) represents the filtered feedback compensation current output value in the kth control cycle within the current motion cycle, I fb_filt (k-1) is the filtered feedback compensation current output value of the (k-1)th control cycle in the current motion cycle, which is calculated from the previous control cycle in the current motion cycle;

[0136] Step 4.3: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] I fb_filt With the set value I of the holding current hold Summing yields the preset current value I. preset ;

[0137] The processed feedforward compensation current The processed feedback compensation current I fb_filt With the set value I of the holding current hold Summing yields the current preset value I for the current control cycle within the current motion cycle. preset :

[0138] (8)

[0139] Among them, I preset (k) is the preset value of the current given in the kth control cycle within the current motion cycle; I is the feedforward compensation current output value after ramp rate limiting processing for the k-th control cycle within the current motion cycle; fb_filt(k) represents the filtered feedback compensation current output value in the kth control cycle within the current motion cycle; I hold To maintain the current setpoint, I hold The typical range of values ​​for I is run 10% to 20%.

[0140] Step 5: Within the control cycle of each motion cycle, based on the current winding temperature T and load rate η, match with the current temperature-load constraint table to obtain the maximum current threshold I under the current operating condition. limit ; take I preset with I limit The minimum of the two values ​​is used as the final current setpoint I for the current control cycle. final ;

[0141] To address the current command optimization requirements of stepper motor systems under varying winding temperatures and load conditions, this invention introduces a dynamic current command threshold adjustment mechanism based on temperature-load dual constraints: the maximum current threshold I for the current control cycle is dynamically determined by querying a pre-configured temperature-load constraint table based on the current winding temperature T and load rate η. limit The obtained current is given a preset value I. preset with I limit Compare the two values ​​and take the smaller value as the final current setpoint I. final This enables adaptive control of motor winding temperature rise and dynamic adaptation to load conditions. The current setpoint optimization process based on temperature-load constraints is as follows: Figure 5 As shown.

[0142] Step 5 specifically includes the following steps:

[0143] Step 5.1: Using the current winding temperature T and load rate η as lookup table indices, match them in the current temperature-load constraint table with a two-dimensional lookup table structure to obtain the corresponding current threshold coefficient. ;

[0144] The temperature-load constraint table in this embodiment is shown in Table 1.

[0145] Table 1 Temperature-Load Constraint Table

[0146]

[0147] Where T is the winding temperature; η is the load factor; This is the current threshold coefficient when the winding temperature is T and the load factor is η;

[0148] In this embodiment, the maximum temperature threshold for the winding is 140°C. The current threshold coefficient... The relationship between winding temperature T and load factor η is as follows:

[0149] (1) When the winding temperature T increases, the current threshold coefficient The maximum current threshold decreases monotonically as the temperature rises, thus suppressing further accumulation of winding temperature rise.

[0150] (2) When the load factor η increases, the current threshold coefficient Monotonically increasing, the maximum current threshold increases with the load, providing a current margin for heavy-load conditions, thereby ensuring that the motor does not lose steps;

[0151] (3) When the winding temperature T is low and the load factor η is high, the current threshold coefficient Allowing values ​​greater than 1 to make the maximum current threshold I limit Exceeding the motor's rated current I rated This provides short-term overload capability;

[0152] (4) When the winding temperature T exceeds the limit temperature threshold, the current threshold coefficient Set to zero to achieve motor thermal protection.

[0153] Step 5.2: Calculate the maximum current threshold I in the current control cycle within the current motion cycle based on the current threshold coefficient γ. limit :

[0154] (9)

[0155] Among them, I rated This is the rated current of the motor; This represents the current threshold coefficient corresponding to the current winding temperature T and load rate η under the current operating conditions.

[0156] Step 5.3: Set the current to a preset value I preset With the maximum current threshold I limit Compare the two values ​​and take the minimum value as the final current setpoint I. final ,Right now:

[0157] (10)

[0158] When the current is given a preset value I preset The maximum current threshold I was not exceeded. limit At that time, the final current setpoint I final Equal to the current given preset value I preset Temperature-load constraints have no effect; when the current is given a preset value I preset Exceeding the maximum current threshold I limit At that time, the final current setpoint I final Limited to the maximum current threshold I limitThis enables adaptive control of winding temperature rise and dynamic adaptation to load conditions.

[0159] Step 5.4: Within each control cycle of a motion cycle, adjust the current threshold coefficient based on the current winding temperature. Perform real-time correction to obtain the corrected current threshold coefficient. ;

[0160] The initial temperature-load constraint table is pre-configured manually; after this preset initial temperature-load constraint table is put into operation, it supports online self-correction updates based on feedback from the actual temperature rise rate, such as... Figure 9 As shown, the update method is as follows:

[0161] During motor operation, the winding temperature of the current control cycle within the motion cycle is acquired, and the winding temperature rise rate dT / dt is calculated in real time; when the winding temperature rise rate exceeds the preset temperature rise rate threshold (dT / dt)... th At that time, for the current operating point Current threshold coefficient Perform a downward adjustment to obtain the corrected current threshold coefficient. Similarly, when the temperature rise rate is below the threshold, the current threshold coefficient can be moderately increased (but the increased value should be adjusted accordingly). (Not exceeding the initial value of the corresponding operating point in the initial constraint table), thus achieving bidirectional adaptive adjustment of the current threshold.

[0162] Specifically, this is achieved through the following formula:

[0163] (11)

[0164] in, Current operating point The corrected current threshold coefficient; dT / dt is the current operating point. The rate of temperature rise of the winding; (dT / dt) th Current operating point The preset winding temperature rise rate threshold is preferably (dT / dt). th =2℃ / s; μ is the correction step size coefficient, typically ranging from 0.01 to 0.05.

[0165] Step 5.5: Obtain the final current setpoint I final The output is sent to the stepper motor driver to drive the motor to perform the motion of the current control cycle.

[0166] Special note: A one-time gradual transition mechanism after the initial operation phase ends;

[0167] At the end of the initial running phase (i.e., step 2.3 completes k) a (1) The immediate neighbor N after the initial identificationtrans Within each control cycle, the final current setpoint I final A one-time gradual transition is performed to prevent the drive current from exceeding the preset operating current I during the initial operation phase. run Directly switch to k-based a (1) Calculated I final A current step surge is generated during the transition to ensure a smooth switching process. The actual output current setpoint I during the transition period. trans Calculate using the following formula:

[0168] (12)

[0169] Where β(k) is the transition coefficient, during the preset transition period N. trans The value increases linearly from 0 to 1 within each control cycle; N trans In this embodiment, 20 control cycles (corresponding to 10ms) are preferred. For the first The actual output current setpoint for each control cycle; For the first The preset operating current for each control cycle; For the first The final current setpoint for each control cycle.

[0170] After the gradual transition is completed, and starting from the nth (n≥2)th motion cycle, due to k a (n) has been continuously and smoothly updated within the cycle, the current setpoint changes continuously, gradual transition is no longer enabled, and the final current setpoint I... final Output directly to the driver.

[0171] Step 6: During normal operation, the target acceleration a is calculated based on the current motion cycle within each motion cycle. target (n) Calculate the latest feedforward compensation coefficient k a (n);

[0172] During normal operation, this step is performed only within the identification window of each motion cycle (n≥2); after completion, the identified k a (n) Takes effect immediately in step 3.1 of the next control cycle.

[0173] Step 6 specifically includes the following steps:

[0174] Step 6.1: Calculate the average shaft-end output torque during the acceleration phase of the current motion cycle. and the average shaft end output torque during the constant speed segment ;

[0175] During the acceleration phase of the current nth motion cycle, the shaft-end output torque sequence of all control cycles within the acceleration phase is collected, and the average shaft-end output torque of the acceleration phase is calculated. During the uniform velocity segment of the current nth motion cycle, collect the data from the first N segments of the uniform velocity segment. c The sequence of shaft-end output torque for each control cycle is calculated, and the average shaft-end output torque during the constant speed segment is also calculated. In this embodiment, N is preferred. c =200 (corresponding to a 100ms sampling window).

[0176] Step 6.2: Collect the target acceleration a during the current motion cycle. target (n) as a regression variable ,based on and The observed value y(n) for the current motion cycle is calculated using the following formula:

[0177] (13)

[0178] Where y(n) is the observation of the nth motion cycle, and n is the motion cycle number; The average shaft-end output torque during the acceleration phase of the nth motion cycle; K represents the average shaft-end output torque during the uniform speed segment of the nth motion cycle. T The torque coefficient can be determined by the parameters of the selected stepper motor; a target (n) represents the target acceleration in the nth motion cycle; is the regression variable for the nth motion cycle.

[0179] Step 6.3: Based on regression variables Calculate the recursive gain K for the current motion cycle. n (n), Calculate the latest feedforward compensation coefficient k based on the observed y(n). a (n) and based on the recursive gain K n (n) Update the current motion cycle k a The estimation error covariance P(n) of (n);

[0180] Calculate the recursive gain K for the current motion cycle. n (n), the formula is as follows:

[0181] (14)

[0182] Among them, K n (n) represents the recursive gain of the nth motion cycle, where n is the motion cycle number; P(n-1) represents the (n-1)th motion cycle. The estimation error covariance; λ is the forgetting factor, preferably λ=0.98.

[0183] Update the feedforward compensation coefficient k according to the following recursive formula. a :

[0184] (15)

[0185] Among them, K n (n) represents the recursive gain for the nth motion cycle; k a (n) is the feedforward compensation coefficient for the nth motion cycle; Let be the regression variable for the nth exercise cycle; y(n) be the observation for the nth exercise cycle; k a (n-1) represents the feedforward compensation coefficient obtained during the (n-1)th motion cycle; when n=2, k a (1) Provided by the single differential identification results of step 2.2.

[0186] Update the current exercise cycle The estimated error covariance P(n) is used, and the updated P(n) is used for recursive least squares identification in the next motion cycle:

[0187] (16)

[0188] Where λ is the forgetting factor, preferably λ=0.98; P(n) is the k of the nth motion cycle. a The estimation error covariance of (n); K n (n) represents the recursive gain for the nth motion cycle; The regression variable for the nth motion cycle is equal to the target acceleration a. target (n); For the (n-1)th motion cycle The estimation error covariance.

[0189] Step 6.4: From completing k a (n) Starting from the next control cycle after identification, k a (n) participates in the calculation of the current setpoint;

[0190] k obtained from identification a (n) Replace the original k a (n-1), used as the feedforward compensation coefficient for the remaining control cycle of the current motion cycle, participates in the calculation of the current setpoint in steps 3 to 5; at the same time, k is saved. a P(n) and P(n) are used for the next motion cycle.

[0191] Step 7: During normal operation, determine whether the current motion cycle has ended; when the current motion cycle ends, determine the k obtained from the current motion cycle identification. aP(n) and P(n) serve as the initial parameters for the next motion cycle, preparing for the start of the next motion cycle;

[0192] Determine whether the number of control cycles in the current motion cycle has reached the total number N of control cycles corresponding to the motion cycle. cp In this embodiment, N cp =10000.

[0193] (1) If not, proceed to the next control cycle;

[0194] (2) If so, complete the entire calculation process for the current motion cycle and use the k obtained from the current motion cycle identification. a P(n) and P(n) serve as the initial parameters for the next motion cycle, preparing for the start of the next motion cycle.

[0195] In summary, the following conclusions can be drawn: This invention achieves dynamic optimization of the stepper motor current setting by combining feedforward compensation current and feedback compensation current, dynamically adjusting the current threshold under temperature-load current constraints, and recursively identifying and updating the feedforward compensation coefficient. Compared with traditional constant current drive methods, this invention significantly reduces operating current and winding temperature rise while ensuring the motor does not lose steps, thereby improving the energy efficiency and operational reliability of the motor system.

[0196] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A method for optimizing the current setting of a stepper motor based on load and temperature constraints, characterized in that, The method includes: Each motion cycle of a stepper motor is defined as consisting of multiple control cycles, and each motion cycle includes an acceleration segment and a constant speed segment; Obtain the stepper motor's shaft-end output torque, winding temperature, and target acceleration for each control cycle. a target ; The method also includes: According to the preset operating current setpoint I run Drive the stepper motor into the initial operation phase and calculate the feedforward compensation coefficient obtained from the first identification. k a (1); The calculation of the feedforward compensation coefficient obtained from the first identification k a (1), including: Step 2.1: Collect the shaft-end output torque sequence for all control cycles during the acceleration phase of the initial operation phase, and then calculate the average shaft-end output torque during the acceleration phase of the initial operation phase. ; Data collection during the initial uniform speed phase before... N c The shaft-end output torque sequence of each control cycle is used to calculate the average shaft-end output torque during the constant speed segment in the initial operation phase. ; Step 2.2: Based on and The feedforward compensation coefficients obtained from the initial identification were calculated using the single-difference method. k a (1) The specific calculation formula is as follows: ； in, K T This is the torque coefficient; a target (1) is the target acceleration for the first motion cycle; From obtaining k a (1) The next control cycle after which the system enters the normal operation phase; Based on the current feedforward compensation coefficient, the feedforward compensation coefficient is updated using a cycle-by-cycle recursive identification algorithm during normal operation. The method of updating the feedforward compensation coefficients using a cycle-by-cycle recursive identification algorithm during normal operation includes: Step 6.1: In the current... n During the acceleration phase of each motion cycle, the shaft-end output torque sequence for all control cycles within the acceleration phase is collected, and the average shaft-end output torque during the acceleration phase is calculated. ; in the current number n The uniform velocity segment of each motion cycle, before the uniform velocity segment is collected. N c The sequence of shaft-end output torque for each control cycle is calculated, and the average shaft-end output torque during the constant speed segment is also calculated. ; Step 6.2: Target acceleration in the current motion cycle a target ( n ) as a regression variable ,based on and Calculate the observations of the current motion cycle y ( n Specifically, this is achieved through the following formula: ； in, n The sequence number of the motion cycle; For the first n Average shaft-end output torque during the acceleration phase of the motion cycle; For the first n Average shaft-end output torque during the constant-speed segment of the motion cycle; K T This is the torque coefficient; a target ( n ) is the first n The target acceleration for each motion cycle; For the first n Regression variables for each motion cycle; Step 6.3: Based on regression variables Calculate the recursive gain for the current motion cycle. K n ( n Based on observations y ( n Calculate the latest feedforward compensation coefficients. k a ( n and based on recursive gain K n ( n Update the current exercise cycle. estimation error covariance P ( n ); The regression variable Calculate the recursive gain for the current motion cycle. K n ( n Specifically, this is achieved through the following formula: ； in, K n ( n ) is the first n The recursive gain per motion cycle, n The sequence number of the motion cycle; P ( n -1) is the first n -1 exercise cycle The estimation error covariance; λ Forgetting factor; The observation-based y ( n Calculate the latest feedforward compensation coefficients. k a ( n Specifically, this is achieved through the following formula: ； in, K n ( n ) is the first n The recursive gain per motion cycle, n ≥2; k a ( n ) is the first n Feedforward compensation coefficient for each motion cycle; For the first n Regression variables for each motion cycle; y ( n ) is the first n Observations for each motion cycle; k a ( n -1) is the first n -Feedforward compensation coefficients obtained from identifying one motion cycle; The recursive gain-based K n ( n Update the current exercise cycle estimation error covariance P ( n Specifically, this is achieved through the following formula: ； in, λ Forgetting factor; P ( n ) is the first n One exercise cycle k a ( n The estimation error covariance, the estimation error covariance P initial value P (1) is a pre-defined positive number; K n ( n ) is the first n The recursive gain for each motion cycle; For the regression variable in the nth motion cycle; For the first n -1 exercise cycle The estimation error covariance; In each control cycle during normal operation, the following steps are performed: According to the current a target Calculate the feedforward compensation current using the feedforward compensation coefficient. I ff Calculate the feedback compensation current based on the current shaft end output torque. I fb and load rate η ;based on I ff and I fb Calculate current given preset value I preset ; Based on the current winding temperature and η Matching it with the current temperature-load constraint table, the maximum current under the current operating condition is obtained. threshold I limit ;Pick I preset and I limit The minimum of the two values ​​is used as the final current setpoint for the current control cycle. I final .

2. The stepper motor current setting optimization method based on load and temperature constraints according to claim 1, characterized in that, The initial operation phase is the identification window phase of the first motion cycle, that is, the operation phase from the first start of the motor to the end of the identification window of the first motion cycle; The identification window phase consists of the entire acceleration phase within the motion cycle and the preceding constant velocity phase within the motion cycle. N c The control cycle consists of several phases; within the identification window of each motion cycle, the feedforward compensation coefficient is adjusted. k a Online identification is performed, and the identification results take effect immediately for the remainder of the current motion cycle, and are used to calculate the feedforward compensation current.

3. The stepper motor current setting optimization method based on load and temperature constraints according to claim 2, characterized in that, According to the current a target Calculate the feedforward compensation current using the feedforward compensation coefficient. I ff , include: Step 3.1: Based on the target acceleration of the stepper motor a target and the latest feedforward compensation coefficient k a Calculate the feedforward compensation current I ff Specifically, this is achieved through the following formula: ； in, I ff ( k ) is the th in the current motion cycle k Feedforward compensation current for each control cycle; a target ( k ) is the th in the current motion cycle k The target acceleration for each control cycle K T The torque coefficient is denoted as ; in the . n Before the end of the motion cycle identification window phase, the latest feedforward compensation coefficient is taken from the feedforward compensation coefficient obtained in the previous motion cycle identification. k a ( n -1), in the n After the motion cycle identification window phase ends, the latest feedforward compensation coefficient is obtained from the current motion cycle identification. k a ( n ).

4. The stepper motor current setting optimization method based on load and temperature constraints according to claim 1, characterized in that, The feedback compensation current is calculated based on the current shaft end output torque. I fb and load rate η ,include: Step 3.2: Calculate the load rate change between adjacent control cycles within the current motion cycle. The specific calculation formula is as follows: ； in, For the current movement cycle, the first Load rate per control cycle; For the current movement cycle, the first Load rate per control cycle; For the current movement cycle, the first The first control cycle and the adjacent first The change in load rate between control cycles; Step 3.3: Define based on load rate η Piecewise nonlinear mapping function The details are as follows: ； in, η 1 and η 2 represents the load rate segmentation threshold; k 1. k 2 and k 3 represents the gain coefficient; I run The preset initial operating current, and I run Less than or equal to rated current I rated ; Step 3.4: Based on and Calculate the feedback compensation current I fb The specific calculation formula is as follows: ； in, I fb ( k ) represents the feedback compensation current for the kth control cycle within the current motion cycle; Based on load rate η The piecewise nonlinear mapping function, i.e., the piecewise mapping component based on the load rate; This represents the change in load rate between the k-th control cycle and the (k-1)-th control cycle within the current motion cycle. k d The differential gain coefficient; For the load rate-based differential feedforward component of the k-th control cycle within the current motion cycle; It is an advance compensation given after predicting the sudden change trend of load rate between adjacent control cycles, which is used to improve the dynamic response speed to load changes.

5. The stepper motor current setting optimization method based on load and temperature constraints according to claim 4, characterized in that, The basis I ff and I fb Calculate current given preset value I preset , include: Step 4.1: Adjust the feedforward compensation current I ff The slope rate of change speed limiting process is applied to obtain the processed feedforward compensation current. The feedforward compensation current change in each control cycle is limited to not exceeding the preset maximum current change rate Δ. I max Specifically, this is achieved through the following formula: ； in, I ff ( k ) is the th in the current motion cycle k Feedforward compensation current for each control cycle; For the current movement cycle, the first k The feedforward compensation current output value after slope rate limiting processing for each control cycle. For the current movement cycle, the first k -1 control cycle of feedforward compensation current output value after slope rate of change speed limiting; Step 4.2: Adjust the feedback compensation current value I fb Perform a first-order low-pass filter to obtain the filtered feedback compensation current output value. I fb_filt Specifically, this is achieved through the following formula: ； in, α These are the filter coefficients; I fb ( k ) is the th in the current motion cycle k Feedback compensation current for each control cycle I fb_filt ( k ) is the th in the current motion cycle k The feedback compensation current output value after filtering in each control cycle. I fb_filt ( k -1) represents the th iteration within the current motion cycle. k -1 control cycle filtered feedback compensation current output value; Step 4.3: Process the feedforward compensation current Feedback compensation current after processing I fb_filt With the set value of the holding current I hold Summing yields the current preset value for the current control cycle within the current motion cycle. I preset .

6. The stepper motor current setting optimization method based on load and temperature constraints according to claim 1, characterized in that, The basis is the current winding temperature and η Matching it with the current temperature-load constraint table, the maximum current threshold under the current operating condition is obtained. I limit ,include: Step 5.1: Set the current winding temperature T and load rate η As a lookup index, it is matched in the current temperature-load constraint table with a two-dimensional lookup table structure to obtain the corresponding current threshold coefficient. ; Step 5.2: Based on the current threshold coefficient Calculate the maximum current threshold of the current control cycle within the current motion cycle. I limit The specific calculation formula is as follows: ； in, I rated This is the rated current of the motor; Current winding temperature T With load rate η The corresponding current threshold coefficient under the operating conditions T For winding temperature, η This refers to the load rate.

7. The stepper motor current setting optimization method based on load and temperature constraints according to claim 6, characterized in that, The method also includes: the temperature-load constraint table is pre-configured manually; after the preset temperature-load constraint table is put into operation, the temperature-load constraint table supports online self-correction and updating, and the specific updating method includes: During motor operation, the winding temperature of the current control cycle within the current motion cycle is acquired, and the temperature rise rate of the winding is calculated in real time. dT / dt When the temperature rise rate of the winding exceeds the preset temperature rise rate threshold ( dT / dt ) th At that time, for the current operating point Current threshold coefficient Perform a downward adjustment to obtain the corrected current threshold coefficient. Similarly, when the temperature rise rate is below the threshold, the current threshold coefficient can be increased, but the increased value will... The current threshold is adjusted bidirectionally and adaptively without exceeding the initial value of the operating point corresponding to the temperature-load constraint table. This is achieved through the following formula: ； in, Current operating point Corrected current threshold coefficient; dT / dt Current operating point The rate of temperature rise of the winding; dT / dt ) th Current operating point Preset winding temperature rise rate threshold; μ To correct the step size coefficient.

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