Improved driving motor power derating strategy and rotating speed control method

Abstract

The invention discloses an improved driving motor power derating strategy and a rotating speed control method, and relates to the technical field of driving motor control, and the method comprises the steps: collecting the actual rotating speed T0 of each period in real time, when T0 is greater than or equal to Tb, reporting an alarm flag bit, and starting to calculate a derating coefficient k in real time, the derating coefficient k output at each moment is the minimum value of the current moment and the previous moment; when T0 reaches the maximum value in the interval from Tb to Ta, the derating coefficient k reaches the minimum value kmin; when T0 is within the interval from Tc to Tb, k keeps kmin unchanged; when T0 is within the interval from Td to Tc, calculating a derating coefficient k in real time, wherein the derating coefficient k output at each moment is the maximum value of the current moment and the previous moment; and when T0 is smaller than or equal to Td, the derating coefficient is recovered to 1, and the alarm flag bit is recovered. According to the derating strategy and the rotating speed control method, the problems that the derating coefficient fluctuates back and forth, and the alarm flag bit and the derating action are not unified are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of drive motor control, and particularly relates to an improved drive motor power derating strategy and speed control method. Background Art

[0002] At present, as a core component of new energy vehicles, the drive motor system determines the vehicle's power performance. With increasingly stringent requirements for drivability and comfort at the vehicle level, the comprehensive performance requirements for the drive motor system are getting higher and higher. To protect the drive motor system to work within a safe range, for some low-level faults (such as motor speed alarm, motor temperature over-temperature alarm, and bus voltage over-voltage alarm, etc.), the output power of the drive motor is usually derated based on the current working condition; however, while derating, it is required that the power derating strategy of the drive motor cannot cause a sudden change in the output torque and thus affect the vehicle's driving performance. Therefore, the power derating strategy of the drive motor is particularly important.

[0003] In related technologies, traditional power derating strategies are all based on target signals (such as actual speed signals), and calculate the real-time derating coefficient from 0 to 1 in real time and directly output it. For example, if the actual speed signal is 10,000 rpm and the calculated real-time derating coefficient is 0.7, then the actual torque output value corresponding to the actual speed signal is multiplied by 0.7 when outputting.

[0004] However, the traditional power derating strategy has the following defects:

[0005] ① Different from the very stable operating conditions of bench tests, the actual operating conditions of the vehicle (including the actual speed signal) are changing in real time, which results in the calculated derating coefficient fluctuating back and forth (see Figure 1 ), thus causing fluctuations in the actual torque output value, and ultimately manifesting as abnormal jitter during vehicle operation, seriously affecting the drivability and comfort of the whole vehicle, which is unacceptable for the whole vehicle.

[0006] ② The traditional derating strategy does not set a hysteresis interval, and there will be a phenomenon of frequent jumping near the speed corresponding to the alarm flag bit. More seriously, there is a phenomenon that the alarm flag bit is not cleared but the derating coefficient has returned to 1. The non-uniformity of the alarm flag bit and the derating action will also have an adverse impact on the control of the VCU, such as the inability to execute instructions normally. Summary of the Invention

[0007] The present application provides an improved drive motor power derating strategy and speed control method to solve the problems of fluctuating derating coefficient and non-uniformity between the alarm flag bit and the derating action.

[0008] In the first aspect, an embodiment of the present application provides an improved drive motor power derating strategy, including the following steps:

[0009] Establish a rotational speed - derating factor coordinate system, set the starting point of the derating interval (Tb, 1), the ending point of derating recovery (Td, 1), and the ending point of the derating interval (Ta, 0), where Ta > Tb > Td, to form a derating linear function; set the slope of the recovery linear function containing (Td, 1) as ε;

[0010] Real - time collect the actual rotational speed T0 of each cycle. When Tb ≤ T0 < Ta, report an alarm flag bit, calculate the derating factor k in real - time according to the derating linear function, calculate the actual torque output value related to the actual rotational speed according to the k, and the derating factor k at each moment takes the minimum value of the derating factor at the current moment and the previous moment until T0 reaches the maximum speed within the interval from Tb to Ta, and the derating factor k remains unchanged; meanwhile, obtain the starting point of derating recovery (Tc, kmin), where kmin is the minimum derating factor corresponding to the maximum speed reached by T0 when Tb ≤ T0 < Ta; calculate Tc according to (Td, 1), ε, and kmin;

[0011] Keep k as kmin unchanged until T0 decreases to Tc, and then calculate the derating factor k in real - time according to the recovery linear function, calculate the actual torque output value related to the actual rotational speed according to the k, and compare the derating factor k at each moment with the derating factor of the previous moment and take the larger value.

[0012] Combined with the first aspect, in one implementation, when T0 ≥ Ta obtained at a certain moment, the derating factor takes zero;

[0013] After calculating the derating factor k in real - time according to the recovery linear function, when T0 < Td obtained at a certain moment, eliminate the alarm flag bit, and the derating factor k returns to 1.

[0014] Combined with the first aspect, in one implementation, Tc is between Td and Tb; the slope of the derating linear function is equal to the negative slope, or the absolute value of the negative slope ε is less than the absolute value of the slope of the derating linear function.

[0015] Combined with the first aspect, in one implementation, there is also a holding linear function between the derating linear function and the recovery linear function; keeping k as kmin unchanged until T0 decreases to Tc includes:

[0016] After T0 reaches the maximum value, T0 decreases. At this time, the derating factor k takes values according to the holding linear function, keeps kmin unchanged until T0 decreases to Tc.

[0017] Combined with the first aspect, in one implementation, when Tb ≤ T0 < Ta, report an alarm flag bit and execute the derating step, and the derating step includes:

[0018] Calculate the derating coefficient k in real time according to the derating linear function, and limit k between 0 and 1;

[0019] Judge in real time whether the derating coefficient at the current moment is less than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment.

[0020] Combined with the first aspect, in an implementation manner, when T0 decreases to Tc, execute the recovery step, and the recovery step includes:

[0021] Judge whether T0 is higher than Td, if not, eliminate the alarm flag bit, and the derating coefficient is restored to 1; if so, go to the next step;

[0022] Calculate the derating coefficient k in real time according to T0 and the recovery linear function, and limit k between 0 and 1;

[0023] Judge in real time whether the derating coefficient at the current moment is greater than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment.

[0024] In the second aspect, an embodiment of the present application provides a speed control method based on the above-mentioned driving motor power derating strategy, including the following steps:

[0025] T0 increases, when Tb ≤ T0 is reached, report the alarm flag bit; calculate the derating coefficient k in real time according to the derating linear function, and calculate the actual torque output value related to the actual speed according to k;

[0026] The actual torque output value decreases, the acceleration changes from a positive value to zero, T0 reaches the maximum value, and the minimum derating coefficient kmin is obtained according to T0 combined with the derating linear function; calculate Tc according to (Td, 1), ε and kmin, and a recovery linear function is formed between (Tc, x) and (Tb, 1);

[0027] T0 starts to decrease, the derating coefficient k remains kmin unchanged until T0 decreases to Tc, calculate the derating coefficient k in real time according to the recovery linear function, the k value starts to increase, and T0 continues to decrease;

[0028] Until T0 < Td, eliminate the alarm flag bit, and the derating coefficient is restored to 1.

[0029] Combined with the second aspect, in an implementation manner, after the step of until T0 < Td, eliminate the alarm flag bit, and the derating coefficient is restored to 1, it further includes:

[0030] The vehicle resumes normal operation and travels normally between the derating interval starting point (Tb, 1) and the derating recovery end point (Td, 1); if Tb ≤ T0 is reached, report the alarm flag bit again.

[0031] In combination with the second aspect, in one embodiment, Tc is between the two values of Td and Tb; the slope of the derating linear function is equal to the negative slope, or the absolute value of the negative slope ε is less than the absolute value of the slope of the derating linear function.

[0032] In combination with the second aspect, in one embodiment, the derating strategy includes a derating step and a recovery step. The derating step includes:

[0033] Calculate the derating coefficient k in real time according to the derating linear function, and limit k between 0 and 1; judge in real time whether the derating coefficient at the current moment is less than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment.

[0034] The recovery step includes:

[0035] Judge whether T0 is higher than Td. If not, eliminate the alarm flag bit and restore the derating coefficient to 1; if so, go to the next step.

[0036] Calculate the derating coefficient k in real time according to T0 and the recovery linear function, and limit k between 0 and 1; judge in real time whether the derating coefficient at the current moment is greater than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment.

[0037] During the derating step, T0 first increases and then decreases; during the recovery step, T0 continues to decrease.

[0038] The beneficial effects brought by the technical solution provided by the embodiment of the present application at least include:

[0039] For the derating strategy of this application, when Tb ≤ T0 < Ta, an alarm flag bit is reported, and the derating coefficient k is calculated in real time according to the derating linear function. The change of the derating coefficient k is gentle. At the same time, within the derating range of Tb ≤ T0 < Ta, the derating coefficient k at each moment takes the minimum value of the derating coefficients at the current moment and the previous moment. The derating coefficient k only decreases and does not increase, solving the technical problem that the derating coefficient fluctuates back and forth, making the vehicle operation more stable and comfortable; further, the derating recovery starting point (Tc, kmin) is dynamically set, where kmin is the minimum derating coefficient corresponding to the maximum speed reached by the vehicle within the derating range of Tb ≤ T0 < Ta, and Tc is calculated based on (Td, 1), ε, and kmin, meeting various scenarios with different initial rotational speeds and having wide applicability; during the process of keeping k unchanged at kmin, it is equivalent to always maintaining the maximum derating efficiency. No matter how T0 changes in the middle, it will slowly decrease to Tc, and then the derating coefficient k is calculated in real time according to the recovery linear function. According to the set slope, the derating coefficient k only increases and does not decrease, and slowly approaches 1; until T0 is less than Td, the alarm flag bit is eliminated and k returns to 1; for the derating strategy of this application, throughout the process, k changes gently according to the set slope, only decreases within the derating range, then remains unchanged, and only increases within the recovery range, preventing back-and-forth fluctuations. The derating coefficient output within the entire alarm range is smooth and has no mutation, and the actual torque output value for controlling the actual rotational speed is very smooth, avoiding the vehicle shake caused by the jitter of the derating coefficient and greatly improving the drivability of the whole vehicle; a special hysteresis loop interval formed by the recovery linear function and the derating linear function is adopted to clarify the opening and ending of the alarm flag bit, effectively unifying the jump of the alarm flag bit and the derating action, and solving the problems of frequent jumping near the rotational speed corresponding to the alarm flag bit and the non-unification of the alarm flag bit and the derating action. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0041] Figure 1 Schematic diagram of the rotational speed-derating coefficient coordinate system for the existing solution (see Figure 1 a) therein) and the schematic diagram of the rotational speed-derating coefficient coordinate system of this application (see Figure 1 b) therein);

[0042] Figure 2 is the flowchart of the derating strategy of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0044] This application provides an improved driving motor power derating strategy, with a gentle change in the derating coefficient, and the vehicle runs stably and comfortably; a special hysteresis interval is set, and the alarm flag bit and the start and end of the derating action are clear and definite, and the actions are highly unified, solving the problems of the derating coefficient fluctuating back and forth and the non-uniformity between the alarm flag bit and the derating action.

[0045] Specifically, as Figure 1 shown, after entering the derating interval in the traditional derating strategy, it is necessary to report the alarm flag bit and execute the derating action. However, due to the absence of a hysteresis interval, there is a phenomenon of frequent jumping near the speed corresponding to the alarm flag bit. For example, when the speed exceeds 10000 rpm (corresponding to Tb), the overspeed alarm flag bit is reported, and when the speed is lower than 9500 rpm (corresponding to Td), the overspeed alarm flag bit disappears. However, the traditional derating strategy does not set a hysteresis interval, so there will be a phenomenon that the alarm flag bit is not cleared but the derating coefficient has returned to 1 near 9500 rpm. The non-uniformity between the flag bit and the derating action will also have an adverse impact on the control of the VCU, such as the inability to execute commands normally.

[0046] To solve the above problems, the derating strategy of this application makes a special setting for the derating coefficient, effectively preventing the derating coefficient from fluctuating back and forth, making the vehicle run more safely and stably, and improving driving performance and comfort; at the same time, a hysteresis interval is set, and the start and end of the alarm flag bit are clear and definite, and the alarm flag bit and the derating action are highly unified.

[0047] As Figure 1 and Figure 2 shown, this application discloses an embodiment of an improved driving motor power derating strategy, which includes the following steps:

[0048] Establish a speed-derating coefficient coordinate system, set the starting point (Tb, 1) of the derating interval and the ending point (Td, 1) of derating recovery, set the ending point (Ta, 0) of the derating interval, and Ta > Tb > Td. A known derating linear function is formed between (Tb, 1) and (Ta, 0). Set the slope of the recovery linear function including the derating recovery ending point (Td, 1) to be ε. Given the derating recovery ending point (Td, 1) and the slope ε, another derating recovery starting point can be determined.

[0049] Obtain the actual speed T0 of the drive motor at different times according to the set period. The time interval between the current moment and the previous moment is one period. When Tb ≤ T0 < Ta (i.e., Figure 1 the derating range of b in

[0050] ), usually when the vehicle is driving and accelerates into the derating range, an alarm flag bit is reported and derating starts to be executed. Calculate the derating coefficient k in real time according to the derating linear function, and calculate the actual torque output value related to the actual speed according to the k. In the derating range of Tb ≤ T0 < Ta, the derating coefficient k at each moment takes the minimum value of the derating coefficients at the current moment and the previous moment. That is, during this process, the derating coefficient k only decreases and does not increase until T0 reaches the maximum speed within the range of Tb to Ta, and the derating coefficient k reaches the minimum value kmin, achieving the maximum derating efficiency, and kmin remains unchanged. At the same time, calculate and obtain the derating recovery starting point as (Tc, kmin), where kmin is the minimum derating coefficient corresponding to the maximum speed reached by the vehicle in the derating range of Tb ≤ T0 < Ta. At this time, the maximum derating efficiency is achieved. Tc is calculated according to (Td, 1), ε, and kmin. A recovery linear function is formed between (Tc, kmin) and (Tb, 1). (Tc, kmin) is a dynamic point obtained according to the actual situation.

[0051] Specifically, the speed control of traditional new energy vehicles is through PI control. Specifically, the actual torque output value for controlling the actual speed is changing with T n to make the actual speed quickly reach the target speed. Among them, U p and U i are respectively the P-term control, i.e., the proportional output term, and the I-term control, i.e., the integral output term, in the PI control. N_err is the difference between the target speed and the actual speed. K p and K i are respectively the proportional coefficient and the integral coefficient of the speed loop controller. is a complex variable and is the integral value for a certain period of time.

[0052] When the derating strategy of this application performs derating control, the actual torque output value for controlling the actual speed is equal to k × T n。The smoother the change of the derating coefficient k, the smaller the fluctuation of the actual torque output value, and the more stable and comfortable the vehicle operation will be. The execution of the derating strategy of this application is mainly through the speed controller. The speed controller can be included in the VCU.

[0053] Specifically, when establishing the speed-derating coefficient coordinate system, multiple different speed-derating coefficient coordinate systems can also be established for different specific scenarios, and derating control is performed according to the set rules to pre-compatibly adapt to low-level faults that may occur in different scenarios (such as motor speed alarm, motor temperature over-temperature alarm, and bus voltage over-voltage alarm, etc.).

[0054] For the derating strategy of this application, when Tb ≤ T0 < Ta, an alarm flag bit is reported, and the derating coefficient k is calculated in real time according to the derating linear function. The change of the derating coefficient k is gentle. At the same time, within the derating interval of Tb ≤ T0 < Ta, the derating coefficient k at each moment takes the minimum value of the derating coefficients at the current moment and the previous moment. The derating coefficient k only becomes smaller and does not become larger, solving the technical problem that the derating coefficient fluctuates back and forth, making the vehicle operation more stable and comfortable;

[0055] Furthermore, the derating recovery starting point (Tc, kmin) is dynamically set. kmin is the minimum derating coefficient corresponding to the maximum speed reached by the vehicle within the derating interval of Tb ≤ T0 < Ta. Tc is calculated based on (Td, 1), ε, and kmin, meeting various scenarios with different initial speeds and having wide applicability;

[0056] During the process when k remains unchanged at kmin, it is equivalent to always maintaining the maximum derating efficiency. No matter how T0 changes in the middle, it will slowly decrease to Tc, and then the derating coefficient k is calculated in real time according to the recovery linear function. According to the set slope, the derating coefficient k only becomes larger and does not become smaller, and slowly tends to 1; until T0 is less than Td, the alarm flag bit is eliminated and k returns to 1; for the derating strategy of this application, throughout the process, k changes gently according to the set slope, only becomes smaller in the derating interval, then remains unchanged, and only becomes larger in the recovery interval, preventing back-and-forth fluctuations. The derating coefficient output in the entire alarm interval is smooth and has no mutation. The actual torque output value that controls the actual speed is very smooth, avoiding the vehicle jitter caused by the derating coefficient jitter and greatly improving the drivability of the whole vehicle;

[0057] Adopting the special hysteresis interval formed by the recovery linear function and the derating linear function clarifies the opening and ending of the alarm flag bit, and effectively unifies the jump of the alarm flag bit and the derating action, solving the problems of frequent jumping near the speed corresponding to the alarm flag bit and the non-unification of the alarm flag bit and the derating action.

[0058] In one embodiment, during the entire derating strategy process, when T0 obtained at a certain moment is ≥ Ta, the derating coefficient is set to zero and the drive motor stops operating. At this time, the rotational speed is too high and it operates under overload, damaging various components. Therefore, for protection, the drive motor stops operating.

[0059] After calculating the derating coefficient k in real time according to the recovery linear function, when T0 obtained at a certain moment is < Td, the alarm flag bit is cleared and the derating coefficient k is restored to 1. At this time, the derating strategy is completely exited and normal operation is restored.

[0060] In one embodiment, Tc is between the two values of Td and Tb; the slope of the derating linear function is equal to the negative slope, that is, the derating linear function and the recovery linear function are two parallel lines.

[0061] In another embodiment, the absolute value of the negative slope ε is less than the absolute value of the slope of the derating linear function, that is, the derating efficiency of the derating linear function is faster than the recovery efficiency of the recovery linear function, achieving rapid derating and slow recovery, and further making the vehicle run smoothly and stably.

[0062] In one embodiment, a holding linear function is also included between the derating linear function and the recovery linear function, that is, corresponding to Figure 1 the holding interval of b in. k remains unchanged at kmin until T0 decreases to Tc, including:

[0063] After T0 reaches the maximum value, T0 decreases. At this time, the derating coefficient k is valued according to the holding linear function and remains unchanged at kmin until T0 decreases to Tc.

[0064] As Figure 2 shown, in one embodiment, when Tb ≤ T0 < Ta, an alarm flag bit is reported and the derating step is executed. The derating step includes:

[0065] Calculating the derating coefficient k in real time according to the derating linear function in combination with the obtained T0, and limiting k between 0 and 1;

[0066] Judging in real time whether the derating coefficient at the current moment is less than the derating coefficient at the previous moment; if so, updating the derating coefficient at the current moment to the calculated value at the current moment; if not, maintaining the derating coefficient at the previous moment.

[0067] Preferably, low-pass filtering and smoothing processing are performed on the derating coefficient to be output, and the derating coefficient is output. The output derating coefficient means that the speed controller outputs the corresponding actual torque output value to the drive motor.

[0068] For the derating strategy of this application, within the derating range where Tb ≤ T0 < Ta, the derating coefficient k at each moment takes the minimum value of the derating coefficients at the current moment and the previous moment. The derating coefficient k only decreases and does not increase, solving the technical problem of the derating coefficient fluctuating back and forth, making the vehicle operation more stable and comfortable.

[0069] Further, when T0 decreases to Tc, a recovery step is executed. The recovery step includes:

[0070] Judge whether T0 is higher than Td. If not, eliminate the alarm flag bit and the derating coefficient is restored to 1; if so, proceed to the next step;

[0071] Calculate the derating coefficient k in real time according to T0 and the recovery linear function, and limit k between 0 and 1;

[0072] Judge in real time whether the derating coefficient at the current moment is greater than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment.

[0073] Further, perform low-pass filtering and smoothing processing on the derating coefficient to be output, and then output the derating coefficient.

[0074] For the derating strategy of this application, when Td ≤ T0 < Ta, according to the set slope, the derating coefficient k only increases and does not decrease, and gradually approaches 1. During the whole process, k changes smoothly according to the set slope, only decreases in the derating range and then remains unchanged, and only increases in the recovery range, preventing back-and-forth fluctuations. The derating coefficient output in the whole alarm range is smooth and has no mutation, and the actual torque output value for controlling the actual speed is very smooth, avoiding the vehicle jitter caused by the derating coefficient jitter, and greatly improving the drivability of the whole vehicle;

[0075] Further, a holding step is also included between the derating step and the recovery step, corresponding to the holding range; the holding step includes:

[0076] Starting from when T0 reaches the maximum speed within the range of Tb to Ta, the derating coefficient k remains kmin unchanged; after that, as T0 decreases, kmin remains unchanged until T0 decreases to Tc. This is the holding step in the middle.

[0077] This application also discloses a speed control method based on the above drive motor power derating strategy, including the following steps:

[0078] The vehicle accelerates, T0 increases, and when Tb ≤ T0 is reached, an alarm flag bit is reported; calculate the derating coefficient k in real time according to the derating linear function, and calculate the actual torque output value related to the actual speed according to the k;

[0079] The drive motor operates according to the actual torque output value. The actual torque output value decreases until the acceleration changes from a positive value to zero. At this time, T0 reaches its maximum value. The minimum derating coefficient kmin is obtained according to T0 in combination with the derating linear function. Tc is calculated based on (Td, 1), ε, and kmin. A recovery linear function is formed between (Tc, x) and (Tb, 1).

[0080] T0 begins to decrease, and the derating coefficient k remains unchanged at kmin until T0 decreases to Tc. The derating coefficient k is calculated in real time according to the recovery linear function. The value of k begins to increase, and T0 continues to decrease.

[0081] Until T0 < Td, the alarm flag bit is cleared, and the derating coefficient is restored to 1.

[0082] In the speed control method of the present application, in the derating interval, when T0 increases, k further decreases for faster derating. After T0 reaches its maximum value, kmin reaches its minimum and remains unchanged. T0 begins to slowly decrease under the action of kmin. In the recovery interval, the decreasing speed of T0 slows down until T0 < Td. Throughout the process, T0 decreases smoothly and orderly without bouncing back and forth, making the vehicle run smoothly and comfortably.

[0083] In one embodiment, until T0 < Td, after the alarm flag bit is cleared and the derating coefficient is restored to 1, it further includes:

[0084] The vehicle resumes normal operation and travels normally between the derating interval start point (Tb, 1) and the derating recovery end point (Td, 1).

[0085] In one embodiment, Tc is between the two values of Td and Tb; the slope of the derating linear function is equal to the negative slope, that is, the derating linear function and the recovery linear function are two parallel lines.

[0086] In another embodiment, the absolute value of the negative slope ε is less than the absolute value of the slope of the derating linear function, that is, the derating efficiency of the derating linear function is faster than the recovery efficiency of the recovery linear function, achieving fast derating and slow recovery, and further making the vehicle run smoothly and stably.

[0087] In one embodiment, the derating strategy includes a derating step and a recovery step.

[0088] When Tb ≤ T0 < Ta, an alarm flag bit is reported, and the derating step is executed. The derating step includes:

[0089] The derating coefficient k is calculated in real time according to the derating linear function, and k is limited between 0 and 1. It is judged in real time whether the derating coefficient at the current moment is less than the derating coefficient at the previous moment. If so, the derating coefficient at the current moment is updated to the calculated value at the current moment. If not, the derating coefficient at the previous moment is maintained.

[0090] When T0 decreases to Tc, a recovery step is executed, and the recovery step includes:

[0091] Determine whether T0 is higher than Td. If not, clear the alarm flag bit and restore the derating factor to 1; if so, proceed to the next step;

[0092] Calculate the derating factor k in real time according to T0 and the recovery linear function, and limit k between 0 and 1; judge in real time whether the derating factor at the current moment is greater than the derating factor at the previous moment; if so, update the derating factor at the current moment to the calculated value at the current moment; if not, keep the derating factor at the previous moment.

[0093] During the derating step, T0 first increases and then decreases. In the recovery step, T0 continues to decrease.

[0094] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0095] It should be noted that in the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0096] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An improved drive motor power derating strategy, characterized in that: The following steps are involved: Establish a speed-derating coefficient coordinate system, set the derating interval starting point (Tb, 1), the derating recovery end point (Td, 1) and the derating interval end point (Ta, 0), Ta>Tb>Td, and form a derating linear function; set the slope of the recovery linear function including (Td, 1) to ε; The actual speed T0 of each cycle is collected in real time. When Tb≤T0<Ta, an alarm flag is reported. The derating coefficient k is calculated in real time according to the derating linear function. The actual torque output value related to the actual speed is calculated according to the k, and the derating coefficient k at each moment takes the minimum value of the derating coefficients at the current moment and the previous moment, until T0 reaches the maximum speed in the interval from Tb to Ta, and the derating coefficient k remains unchanged; at the same time, the derating recovery starting point (Tc, kmin) is obtained, kmin is the minimum derating coefficient corresponding to the maximum speed reached by T0 in Tb≤T0<Ta; Tc is calculated according to (Td, 1), ε and kmin; k remains unchanged at kmin until T0 decreases to Tc, and then the derating factor k is calculated in real time according to the recovery linear function, and the actual torque output value related to the actual speed is calculated according to the k, and the derating factor k at each moment is compared with the derating factor at the previous moment and the larger value is taken.

2. An improved drive motor power derating strategy as claimed in claim 1, characterized in that: When T0≥Ta obtained at a certain moment, the derating factor is zero; After the derating factor k is calculated in real time according to the recovery linear function, when T0<Td obtained at a certain moment, the alarm flag is eliminated and the derating factor k is restored to 1.

3. The improved drive motor power derating strategy according to claim 1, characterized in that: The Tc is between Td and Tb; the slope of the derating linear function is equal to the negative slope, or the absolute value of the negative slope ε is smaller than the absolute value of the slope of the derating linear function.

4. An improved drive motor power derating strategy as claimed in claim 1, characterized in that: A maintaining linear function is also included between the derating linear function and the recovery linear function; the k remains unchanged at kmin until T0 decreases to Tc, including: After T0 reaches the maximum value, T0 decreases. At this time, the derating factor k is taken according to the linear function, keeping kmin unchanged until T0 decreases to Tc.

5. An improved drive motor power derating strategy as claimed in claim 1, characterized in that: When Tb≤T0<Ta, an alarm flag is issued and a derating step is executed, wherein the derating step includes: The derating factor k is calculated in real time according to the derating linear function, and the amplitude k is limited between 0 and 1; Determine in real time whether the current derating coefficient is less than the previous derating coefficient; if so, update the current derating coefficient to the current calculated value; if not, keep the previous derating coefficient.

6. An improved drive motor power derating strategy as claimed in claim 1, characterized in that: When T0 decreases to Tc, a recovery step is performed, the recovery step comprising: Determine whether T0 is higher than Td. If not, clear the alarm flag and restore the derating factor to 1. If yes, proceed to the next step. Calculate the derating factor k in real time based on T0 and the recovery linear function, and limit k between 0 and 1; Determine in real time whether the current derating coefficient is greater than the previous derating coefficient; if so, update the current derating coefficient to the current calculated value; if not, keep the previous derating coefficient.

7. A speed control method based on the drive motor power derating strategy of claim 1, characterized in that: The following steps are involved: T0 increases and reaches Tb≤T0, reporting an alarm flag; calculating the derating coefficient k in real time according to the derating linear function, and calculating the actual torque output value related to the actual speed according to the k; The actual torque output value decreases, the acceleration changes from positive to zero, T0 reaches the maximum value, and the minimum derating coefficient kmin is obtained based on T0 combined with the derating linear function; Calculate Tc according to (Td, 1), ε and kmin, and form a recovery linear function between (Tc, x) and (Tb, 1); T0 starts to decrease, and the derating factor k remains unchanged at kmin until T0 decreases to Tc. The derating factor k is calculated in real time according to the recovery linear function, and the k value starts to increase, and T0 continues to decrease; When T0<Td, the alarm flag is eliminated and the derating factor is restored to 1.

8. The speed control method according to claim 7, characterized in that: The method further includes: until T0<Td, the alarm flag is eliminated, and the derating factor is restored to 1; The vehicle resumes normal operation and runs normally between the starting point of the derating interval (Tb, 1) and the end point of derating recovery (Td, 1); if Tb≤T0 is reached, the alarm flag is reported again.

9. The speed control method according to claim 7, characterized in that: The Tc is between Td and Tb; the slope of the derating linear function is equal to the negative slope, or the absolute value of the negative slope ε is smaller than the absolute value of the slope of the derating linear function.

10. The speed control method according to claim 7, characterized in that: The derating strategy includes a derating step and a recovery step, and the derating step includes: Calculate the derating coefficient k in real time according to the derating linear function, and limit k between 0 and 1; determine in real time whether the derating coefficient at the current moment is less than the derating coefficient at the previous moment; if so, update the derating coefficient at the current moment to the calculated value at the current moment; if not, keep the derating coefficient at the previous moment; The recovery steps include: Determine whether T0 is higher than Td. If not, clear the alarm flag and restore the derating factor to 1. If yes, proceed to the next step. The derating factor k is calculated in real time according to T0 and the recovery linear function, and k is limited between 0 and 1; it is determined in real time whether the derating factor at the current moment is greater than the derating factor at the previous moment; if so, the derating factor at the current moment is updated to the calculated value at the current moment; if not, the derating factor at the previous moment is maintained. During the derating step, T0 first increases and then decreases; during the recovery step, T0 continues to decrease.

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