Vehicle and control method thereof

Abstract

The invention discloses a vehicle and a control method thereof. The vehicle comprises a battery, a controller and an electromagnetic brake. The electromagnetic brake comprises a coil; the controller comprises a switch unit and a control unit; the first end of the coil is connected with the battery, the first end of the switch unit is connected with the second end of the coil, and the second end of the switch unit is connected with first power supply voltage; the control unit is connected with the control end of the switch unit; the control method of the vehicle is executed by the control unit. The vehicle control method comprises the steps that when an electromagnetic brake does not conduct braking, a control signal is output to the control end of a switch unit according to the actual current and reference current of a coil based on a proportional-integral control strategy, so that the voltage of the coil is controlled, and the current of the coil is controlled; wherein the reference current is rated current or holding current of the electromagnetic brake, the holding current is rated current with a preset proportion, and the preset proportion is smaller than 100%. According to the technical scheme, the stability of the electromagnetic brake is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicles, and in particular to a vehicle and a control method thereof. Background Art

[0002] New energy vehicles can include industrial vehicles and road vehicles, etc. The vehicles include electromagnetic brakes, which can replace traditional hand brakes. Electromagnetic brakes are electronically controlled and have the characteristics of no driver intervention and fast response speed. For this reason, they are favored by more and more OEMs.

[0003] The electromagnetic brake includes a coil. When the coil is energized, it attracts the armature (i.e., brake pad) and separates it from the brake disc, allowing the vehicle's drive shaft to run normally without braking. When the coil loses power, it no longer attracts the armature, causing it to press against the brake disc, achieving vehicle braking.

[0004] The vehicle's power battery can power the coil, and whether the coil is powered and the coil's voltage are controlled by the vehicle's controller. However, the coil is an inductive load. When the electromagnetic brake is working, the temperature rises, causing the internal resistance of the coil to change with the temperature, which in turn causes the coil's current to fluctuate greatly, affecting the magnetic force that attracts the armature, making the electromagnetic brake less stable. In addition, the battery voltage may change with the vehicle's load, making the voltage at both ends of the coil unstable, which will also affect the magnetic force that attracts the armature, making the electromagnetic brake less stable. Summary of the invention

[0005] The present invention provides a vehicle and a control method thereof to solve the problem of poor stability of an electromagnetic brake.

[0006] According to one aspect of the present invention, a control method for a vehicle is provided, wherein the vehicle comprises a battery, a controller and an electromagnetic brake; the electromagnetic brake comprises a coil; the controller comprises a switch unit and a control unit; a first end of the coil is connected to the battery, a first end of the switch unit is connected to a second end of the coil, and a second end of the switch unit is connected to a first power supply voltage; the control unit is connected to a control end of the switch unit; the method is executed by the control unit; The method comprises: When the electromagnetic brake is not braking, the actual current of the coil is obtained, and based on a proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current of the coil and a reference current, so as to control the voltage of the coil and the current of the coil; wherein the reference current is the rated current or the holding current of the electromagnetic brake, and the holding current is a preset proportion of the rated current, and the preset proportion is less than 100%.

[0007] Optionally, when the electromagnetic brake is not braking, based on a proportional-integral control strategy, a control signal is output to a control end of the switch unit according to an actual current of the coil and a reference current, including: When the electromagnetic brake is released, based on a proportional-integral control strategy, a control signal is output to a control terminal of the switch unit according to the actual current of the coil and the rated current; After a first preset time, based on a proportional-integral control strategy, a control signal is output to the control terminal of the switch unit according to the actual current of the coil and the holding current.

[0008] Optionally, based on a proportional-integral control strategy, outputting a control signal to a control terminal of the switch unit according to an actual current of the coil and a reference current includes: The product of the difference between the actual current and the reference current and the proportional coefficient is used as the proportional term of the proportional-integral control strategy; The product of the proportional term and the integral coefficient and the sum of the previous integral term of the proportional-integral control strategy are used as the current integral term of the proportional-integral control strategy; Taking the maximum output value and the minimum output value as limit values, the sum of the proportional term and the current integral term is used as the output value of the proportional-integral control strategy, and the control signal corresponding to the output value is output to the control end of the switch unit; wherein the control signal is a pulse width modulation signal, the duty cycle of the pulse width modulation signal corresponding to the maximum output value is 100%, and the duty cycle of the pulse width modulation signal corresponding to the minimum output value is 0.

[0009] Optionally, after outputting a control signal to the control terminal of the switch unit according to the actual current of the coil and the reference current based on the proportional-integral control strategy, the method further includes: When the controller determines that the vehicle fails or receives a failure signal, obtaining a first rotation speed of a motor of the vehicle; After a second preset time period, obtaining a second rotation speed of the motor; If the second rotation speed is in a direction different from the first rotation speed, the electromagnetic brake is controlled to perform braking.

[0010] Optionally, the vehicle further comprises a brake pedal; If the second speed is in a direction different from the first speed, controlling the electromagnetic brake to brake comprises: If the second speed is in a direction different from the first speed and no braking signal from the brake pedal is received after a third preset time period, the electromagnetic brake is controlled to brake.

[0011] Optionally, the vehicle further comprises a brake pedal; If the second speed is in a direction different from the first speed, controlling the electromagnetic brake to brake comprises: If the second speed is in a different direction from the first speed and a brake signal from the brake pedal is received within a third preset time period, acquiring a third speed of the motor at least twice after a fourth preset time period; If the absolute value of the third rotational speed is greater than the absolute value of the first rotational speed for a consecutive preset number of times, the electromagnetic brake is controlled to brake; wherein the preset number of times is greater than 1.

[0012] Optionally, the vehicle further comprises a brake pedal; After outputting a control signal to the control terminal of the switch unit according to the actual current of the coil and the reference current based on the proportional-integral control strategy, the method further includes: When the controller determines that the vehicle fails or receives a failure signal, obtaining a first rotation speed of a motor of the vehicle; If a brake signal from the brake pedal is received within a third preset time period, obtaining a third rotation speed of the motor at least twice after a fourth preset time period; If the absolute value of the third rotational speed is greater than the absolute value of the first rotational speed for a consecutive preset number of times, the electromagnetic brake is controlled to brake; wherein the preset number of times is greater than 1.

[0013] Optionally, after controlling the electromagnetic brake to brake, the method further includes: If the accelerator stroke of the vehicle is greater than a preset stroke, the electromagnetic brake is controlled to stop braking, and after the accelerator stroke is zero, the electromagnetic brake is controlled to brake; wherein the preset stroke is greater than 80% of the maximum stroke of the accelerator.

[0014] Optionally, controlling the electromagnetic brake to brake comprises: A control signal with a zero duty cycle is output to the control terminal of the switch unit.

[0015] According to another aspect of the present invention, a vehicle is provided, the vehicle comprising a battery, a controller and an electromagnetic brake; the electromagnetic brake comprises a coil; the controller comprises a switch unit and a control unit; The first end of the coil is connected to the battery, the first end of the switch unit is connected to the second end of the coil, and the second end of the switch unit is connected to a first power supply voltage; the control unit is connected to the control end of the switch unit; the control unit is used to execute the vehicle control method described in any embodiment of the present invention.

[0016] The technical solution of the embodiment of the present invention is to obtain the actual current of the coil when the electromagnetic brake is not braking, and based on the proportional-integral control strategy, output a control signal to the control end of the switch unit according to the actual current of the coil and the reference current, thereby controlling the conduction time of the switch unit, thereby controlling the time when the second end of the coil is grounded, and then controlling the voltage of the coil, so that the current of the coil changes to the reference current, and the current of the coil is close to or equal to the reference current. In this way, the current of the coil can be controlled in real time according to the actual current of the coil fed back, so that when the current of the coil is affected by the temperature or the battery voltage, the current of the coil can still remain stable, that is, the current of the coil is always close to or equal to the reference current, thereby ensuring that the coil can stably attract the armature, thereby ensuring the stable operation of the electromagnetic brake and improving the stability of the electromagnetic brake.

[0017] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 is a flow chart of a vehicle control method provided by an embodiment of the present invention; Figure 2 is a flow chart of another vehicle control method provided by an embodiment of the present invention; Figure 3 is a flow chart of another vehicle control method provided by an embodiment of the present invention; Figure 4 It is a structural schematic diagram of a vehicle provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] The embodiment of the present invention provides a control method for a vehicle, wherein the vehicle includes a battery, a controller and an electromagnetic brake; the electromagnetic brake includes a coil; the controller includes a switch unit and a control unit; the first end of the coil is connected to the battery, the first end of the switch unit is connected to the second end of the coil, and the second end of the switch unit is connected to a first power supply voltage; the control unit is connected to the control end of the switch unit; and the control method for the vehicle is executed by the control unit. The vehicle may be a new energy vehicle, such as an electric vehicle, or an industrial vehicle, such as a forklift and a shovel. It may also be a road vehicle. The battery may be a power battery of the vehicle. The electromagnetic brake may control the braking of the vehicle, such as when the target speed of the vehicle (or the target speed of the motor) is zero, the electromagnetic brake brakes, thereby achieving automatic braking.

[0023] The controller may be a controller of the whole vehicle, that is, a controller for controlling the motor of the vehicle. The controller includes a switch unit and a control unit, and the control unit may include a control chip, such as a single-chip microcomputer chip or a digital processing chip. The switch unit may include a switch transistor, etc. The first end of the coil is connected to the battery, for example, to the positive pole of the battery, and the second end of the switch unit is connected to the first power supply voltage, which may be a ground voltage. When the switch unit is turned on, the first end of the switch unit is connected to the second end of the switch unit, so that the second end of the coil is grounded, and the coil is energized, the armature is attracted, and the armature is separated from the brake disc, and the electromagnetic brake is in an attracted state, that is, in an unbraked state. When the switch unit is disconnected, the second end of the coil is suspended, the coil loses power, and the armature is no longer attracted, so that the armature presses the brake disc, and the electromagnetic brake is in a braking state. The control unit can control whether the switch unit is turned on, thereby controlling whether the coil is energized, and then controlling whether the electromagnetic brake is braked. In some other embodiments, the first end of the coil may also be connected to the negative pole of the battery, and the first power supply voltage is a positive voltage, which is not limited in this embodiment.

[0024] Figure 1 is a flow chart of a vehicle control method provided by an embodiment of the present invention, with reference to Figure 1 , the vehicle control method includes: S110, when the electromagnetic brake is not braking, obtaining the actual current of the coil.

[0025] Specifically, when the electromagnetic brake is not braking, that is, the coil in the electromagnetic brake is energized, the armature is attracted, and the armature is separated from the brake disc, the control unit in the controller can obtain the actual current of the coil. For example, the control unit obtains the actual current of the coil through a current sensor or a current transformer.

[0026] S120. Based on the proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current of the coil and the reference current to control the voltage of the coil and the current of the coil; wherein the reference current is the rated current or the holding current of the electromagnetic brake, and the holding current is a preset proportion of the rated current, and the preset proportion is less than 100%.

[0027] Among them, the proportional-integral (PI) control strategy can form a control deviation based on the given value and the actual output value, and form a control quantity by linearly combining the deviation in proportion and integral to control the controlled object. Therefore, the proportional-integral control strategy can determine the output value according to the deviation between the actual current of the coil and the reference current, and then determine the control signal output to the control end of the switching unit, so that the current of the coil tends to the reference current. The control signal output by the control unit can be a pulse width modulation (PWM) signal, and the output value of the proportional-integral control strategy is the digital quantity corresponding to the PWM signal. For example, the digital quantity adopts the Q24 format, that is, when the duty cycle of the PWM signal is 100%, the corresponding digital quantity is , when the duty cycle of the PWM signal is 0, the corresponding digital quantity is 0. The duty cycle can be subdivided to achieve more accurate control of the on-time of the switch unit, and thus more accurate control of the voltage of the coil. In some other implementations, the digital quantity can also be in other formats, which is not limited in this embodiment. For example, the digital quantity can also be in Q48 format, that is, when the duty cycle of the PWM signal is 100%, the corresponding digital quantity is , this embodiment does not limit this.

[0028] Specifically, the output value of the proportional-integral control strategy can be adjusted by the actual current and the reference current, so that the control signal output to the control end of the switching unit can be adjusted, thereby controlling the conduction time of the switching unit, thereby controlling the time when the second end of the coil is grounded, and then controlling the average voltage of the coil, and controlling the effective current of the coil, so that the current of the coil changes toward the reference current, and the current of the coil is close to or equal to the reference current.

[0029] By setting the reference current to the rated current or the holding current, the coil can be controlled to different currents according to the braking requirements. For example, when the electromagnetic brake is required to be better attracted, that is, when the coil is required to better attract the armature, the reference current can be set to the rated current, so that the magnetic force of the coil is larger and the armature is better attracted, ensuring that the vehicle's drive shaft can operate normally and avoiding intermittent attraction due to insufficient magnetic force. When the armature is attracted more stably or the power consumption needs to be reduced, the reference current can be set to the holding current. The smaller the holding current, the lower the power consumption can be while ensuring stable attraction.

[0030] The technical solution of this embodiment is to obtain the actual current of the coil when the electromagnetic brake is not braking, and based on the proportional-integral control strategy, output a control signal to the control end of the switch unit according to the actual current of the coil and the reference current, thereby controlling the conduction time of the switch unit, thereby controlling the time when the second end of the coil is grounded, and then controlling the voltage of the coil, so that the current of the coil changes to the reference current, and the current of the coil is close to or equal to the reference current. In this way, the current of the coil can be controlled in real time according to the actual current of the coil fed back, so that when the current of the coil is affected by the temperature or battery voltage, the current of the coil can still remain stable, that is, the current of the coil is always close to or equal to the reference current, thereby ensuring that the coil can stably attract the armature, thereby ensuring the stable operation of the electromagnetic brake and improving the stability of the electromagnetic brake.

[0031] On the basis of the above technical solution, optionally, when the electromagnetic brake is not braking, based on the proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current and the reference current of the coil, including: Step a1: when the electromagnetic brake is released, based on the proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current and the rated current of the coil.

[0032] Specifically, when the brake is just being pulled in (i.e., just after the brake is released), the reference current can be set to the rated current, that is, the output value of the proportional-integral control strategy is adjusted with the rated current as the target, thereby adjusting the control signal output to the switch unit, and then controlling the voltage of the coil, and then controlling the current of the coil, so that the current of the coil is close to or equal to the rated current. This makes the magnetic force of the coil larger, better pulls in the armature, ensures that the vehicle's drive shaft can operate normally, and avoids intermittent pull-in due to insufficient magnetic force.

[0033] Step a2: after a first preset time, based on a proportional-integral control strategy, output a control signal to a control terminal of the switch unit according to the actual current and the maintaining current of the coil.

[0034] Specifically, after the brake is released and stabilized, that is, after the armature is stably attracted, the reference current can be set as the holding current, that is, the output value of the proportional-integral control strategy is adjusted with the holding current as the target, thereby adjusting the control signal output to the switch unit, and then controlling the voltage of the coil, and then controlling the current of the coil, so that the current of the coil is close to or equal to the holding current. A smaller holding current can reduce power consumption while ensuring stable attraction.

[0035] Based on the above technical solutions, Figure 2 is a flowchart of another vehicle control method provided by an embodiment of the present invention. Optionally, refer to Figure 2 , the vehicle control method includes: S210: When the electromagnetic brake is not braking, obtain the actual current of the coil.

[0036] S220: The product of the difference between the actual current and the reference current and the proportional coefficient is used as the proportional term of the proportional-integral control strategy.

[0037] The difference between the actual current and the reference current is the difference between the reference current and the actual current.

[0038] Specifically, by calculating the difference between the actual current and the reference current, the deviation between the actual current of the coil and the reference current can be determined, and the output value of the proportional-integral control strategy is adjusted according to the deviation between the actual current of the coil and the reference current, thereby adjusting the output signal corresponding to the output value so that the current of the coil can be close to or equal to the reference current.

[0039] For example, the reference current is , the actual current is , the proportionality coefficient is , the proportional term is , then the proportional term is .

[0040] S230: taking the product of the proportional term and the integral coefficient and the sum of the previous integral term of the proportional-integral control strategy as the current integral term of the proportional-integral control strategy.

[0041] Specifically, the last integral term of the proportional-integral control strategy is the integral term of the proportional-integral control strategy in the last calculation cycle, and the current integral term of the proportional-integral control strategy is the integral term in the current calculation cycle. Among them, the process of the proportional-integral control strategy outputting an output value according to the input value (actual current and reference current) is a calculation cycle. By determining the current integral term, the cumulative deviation between the actual current and the reference current can be determined, and the output value of the proportional-integral control strategy is adjusted according to the cumulative deviation, so that the current of the coil is closer to the reference current.

[0042] For example, the integral coefficient is , the previous integral term is , the current integral term is , then the current integral term is . Wherein, j is an integer greater than 1.

[0043] S240, taking the maximum output value and the minimum output value as the limit values, taking the sum of the proportional term and the current integral term as the output value of the proportional-integral control strategy, and outputting the control signal corresponding to the output value to the control end of the switch unit to control the voltage of the coil to control the current of the coil; wherein the control signal is a pulse width modulation signal, the duty cycle of the pulse width modulation signal corresponding to the maximum output value is 100%, and the duty cycle of the pulse width modulation signal corresponding to the minimum output value is 0.

[0044] Specifically, the maximum output value and the minimum output value are used as the limit values, and the sum of the proportional term and the current integral term is used as the output value of the proportional integral control strategy, that is, the output value of the proportional integral control strategy is limited to be greater than or equal to the minimum output value, and less than or equal to the maximum output value. By determining the output value of the proportional integral control strategy, the control signal corresponding to the output value can be determined, and then the conduction time of the switch unit can be controlled, thereby controlling the time when the second end of the coil is grounded, and then controlling the average voltage of the coil, so that the current of the coil changes to the reference current, and the current of the coil is close to or equal to the reference current.

[0045] For example, the output value of the proportional-integral control strategy is , then the output value of the proportional-integral control strategy is .

[0046] It can be seen that after the vehicle is turned on, when the electromagnetic brake is not braking, the controller can cyclically obtain the actual current of the coil and continuously execute the proportional-integral control strategy, that is, the control signal output to the control end of the switching unit can be adjusted in real time or periodically according to the actual current of the coil and the reference current, so that the current of the coil is close to or equal to the reference current.

[0047] In this way, the closed-loop regulation of the coil current is achieved through the proportional-integral control strategy. When the actual current of the coil is greater than the reference current, the control unit will reduce the output value of the proportional-integral control strategy, so that the duty cycle of the control signal output to the control end of the switch unit is reduced, the average voltage of the coil is reduced, and the effective current of the coil is reduced. When the actual current of the coil is less than the reference current, the control unit will increase the output value of the proportional-integral control strategy, so that the duty cycle of the control signal output to the control end of the switch unit is increased, the average voltage of the coil is increased, and the effective current of the coil is increased. Therefore, no matter how the inductance or impedance of the coil changes, or how the battery voltage fluctuates, the current of the coil can be kept stable, the magnetic force generated by the coil is stable, the attraction state of the electromagnetic brake is stable, and the stability of the electromagnetic brake is improved.

[0048] On the basis of the above technical solutions, Figure 3 is a flowchart of another vehicle control method provided by an embodiment of the present invention. Optionally, refer to Figure 3 , the vehicle control method includes: S310, when the electromagnetic brake is not braking, obtaining the actual current of the coil.

[0049] S320. Based on the proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current of the coil and the reference current to control the voltage of the coil and the current of the coil; wherein the reference current is the rated current or the holding current of the electromagnetic brake, and the holding current is a preset proportion of the rated current, and the preset proportion is less than 100%.

[0050] S330: When the controller determines that a fault occurs in the vehicle or receives a fault signal, obtain a first rotation speed of a motor of the vehicle.

[0051] Specifically, the vehicle failure may be that the speed of the motor cannot be controlled, or the accelerator fails, etc. The controller may judge whether the vehicle has a fault, determine whether the vehicle has a fault, and may also receive a fault signal from other devices (such as a central controller of the vehicle, etc.). When the controller determines that the vehicle has a fault or receives a fault signal, the first speed of the motor of the vehicle is obtained, and the first speed of the motor when the vehicle fails can be determined.

[0052] S340: After a second preset time period, obtain a second rotation speed of the motor.

[0053] S350: If the second rotation speed is in a direction different from the first rotation speed, control the electromagnetic brake to brake.

[0054] Specifically, if the second speed is different from the first speed in direction, it may be that the vehicle has a fault and has changed from an uphill state to a downhill state, causing the speed direction to change. In this case, the electromagnetic brake is controlled to brake and force the vehicle to stop, thereby preventing the vehicle from sliding downhill. This can avoid the problem that some vehicles do not have a brake pedal and the electromagnetic brake cannot brake when the target speed of the motor is not zero.

[0055] In this way, when the vehicle is driving on a slope and a serious fault suddenly occurs, the vehicle will slide freely along the slope. At this time, due to the influence of gravity, the vehicle speed will become faster and faster, that is, the motor speed will become faster and faster. By controlling the electromagnetic brake to brake, the problem in the related art that the target speed of the motor is not zero and the electromagnetic brake cannot brake automatically can be avoided.

[0056] On the basis of the above technical solution, in some embodiments, optionally, the vehicle further includes a brake pedal; the brake pedal can be pressed by the driver to brake.

[0057] If the second speed is in a direction different from the first speed, the electromagnetic brake is controlled to brake, including: If the second rotation speed is in a direction different from the first rotation speed and no braking signal from the brake pedal is received after a third preset time period, the electromagnetic brake is controlled to brake.

[0058] Specifically, if the second speed is different from the first speed in direction, and no brake signal is received from the brake pedal after the third preset time, that is, after the speed direction of the vehicle changes, the driver does not step on the brake pedal in time, then the control unit of the controller controls the electromagnetic brake to prevent the vehicle from rolling down the slope. By setting the third preset time, time is reserved for the driver to step on the brake pedal, which can avoid misjudgment.

[0059] Optionally, if the second rotational speed is in a direction different from the first rotational speed, controlling the electromagnetic brake to brake includes: Step b1: if the second speed is in a direction different from the first speed and a brake signal from the brake pedal is received within a third preset time period, then the third speed of the motor is acquired at least twice after a fourth preset time period.

[0060] Specifically, if the second speed is in a different direction from the first speed, and a brake signal from the brake pedal is received within the third preset time, that is, after the speed direction of the vehicle changes, the driver promptly steps on the brake pedal, then the third speed of the motor is acquired at least twice after the fourth preset time. The third speed of the motor may be acquired at least twice in succession, or a preset interval may be provided between the two acquisitions of the third speed, which is not limited in this embodiment.

[0061] Step b2: if the absolute value of the third speed for a preset number of consecutive times is greater than the absolute value of the first speed, control the electromagnetic brake to brake; wherein the preset number of times is greater than 1.

[0062] Specifically, if the absolute value of the third speed is greater than the absolute value of the first speed for a continuous preset number of times, and the absolute value of the motor speed is still increasing after the brake pedal is stepped on, it is determined that the brake pedal is faulty and braking is impossible, and the electromagnetic brake is controlled to brake. If the absolute value of the third speed is not greater than the absolute value of the first speed for a continuous preset number of times, the electromagnetic brake is controlled not to brake, that is, the electromagnetic brake is in an engaged state.

[0063] Exemplarily, for example, the preset number of times is 2. After the third speed is obtained for the first time, the relationship between the third speed and the first speed can be determined. If the absolute value of the third speed obtained for the first time is greater than the absolute value of the first speed, the error value is increased by one; after the third speed is obtained for the second time, if the absolute value of the third speed obtained for the second time is greater than the absolute value of the first speed, the error value is increased by one. If the error value reaches the preset number of times, that is, the absolute value of the third speed for the consecutive preset number of times is greater than the absolute value of the first speed, the electromagnetic brake is controlled to brake. If the absolute value of the third speed obtained for the second time is less than or equal to the absolute value of the first speed, the error value is zero, and the counting starts again until the error value reaches the preset number of times, and the electromagnetic brake is controlled to brake. If, among the third speeds collected for multiple times, the absolute value of the third speed for the consecutive preset number of times is not greater than the absolute value of the first speed, the electromagnetic brake is controlled not to brake.

[0064] Optionally, after outputting a control signal to the control terminal of the switch unit according to the actual current of the coil and the reference current based on the proportional-integral control strategy, the method further includes: Step c1: When the controller determines that a fault occurs in the vehicle or receives a fault signal, a first rotation speed of the motor of the vehicle is obtained.

[0065] Step c2: if a brake signal from the brake pedal is received within the third preset time period, then the third rotation speed of the motor is acquired at least twice after the fourth preset time period.

[0066] Specifically, regardless of whether the direction of the motor speed changes, if a brake signal from the brake pedal is received within the third preset time, the third speed of the motor can be acquired at least twice after the fourth preset time. The third speed of the motor can be acquired at least twice in succession, or a preset interval can be provided between the two acquisitions of the third speed, which is not limited in this embodiment.

[0067] Step c3: if the absolute value of the third speed for a preset number of consecutive times is greater than the absolute value of the first speed, control the electromagnetic brake to brake; wherein the preset number of times is greater than 1.

[0068] Specifically, if the absolute value of the third speed is greater than the absolute value of the first speed for a consecutive preset number of times, and the absolute value of the motor speed continues to increase after the brake pedal is pressed, it is determined that the brake pedal is faulty and braking is impossible, then the electromagnetic brake is controlled to brake; if the absolute value of the third speed is not greater than the absolute value of the first speed for a consecutive preset number of times, the electromagnetic brake is controlled not to brake, that is, the electromagnetic brake is in the engaged state.

[0069] Optionally, after controlling the electromagnetic brake to brake, the method further includes: If the accelerator stroke of the vehicle is greater than a preset stroke, the electromagnetic brake is controlled to stop braking, and after the accelerator stroke is zero, the electromagnetic brake is controlled to brake; wherein the preset stroke is greater than 80% of the maximum stroke of the accelerator.

[0070] Specifically, when a vehicle fails and the electromagnetic brake is applied, if the accelerator stroke of the vehicle is greater than a preset stroke, indicating that the driver needs to move the vehicle, the control unit controls the electromagnetic brake to stop braking, that is, sends a control signal with a non-zero duty cycle to the control end of the switch unit, so that the coil is energized to attract the armature, thereby allowing the vehicle to operate normally. In this way, the problem of the vehicle being unable to move after braking, resulting in the problem of the vehicle being parked and obstructing traffic, can be avoided.

[0071] By setting a preset stroke, the electromagnetic brake will be controlled to stop braking only when the vehicle's accelerator stroke is greater than the preset stroke. This can avoid misjudgment and prevent the driver's frequent foot shaking from causing the electromagnetic brake to be repeatedly engaged and released.

[0072] Optionally, controlling the electromagnetic brake to brake includes: A control signal with a zero duty cycle is output to the control terminal of the switch unit.

[0073] Specifically, the output value of the proportional-integral control strategy in the control unit of the controller is zero, so that the control unit outputs a control signal with a duty cycle of zero to the control end of the switch unit, the switch unit is disconnected, and the second end of the coil is suspended, that is, not grounded, so that the coil loses power and the armature is no longer attracted. The armature presses the brake disc to achieve braking of the electromagnetic brake.

[0074] An embodiment of the present invention also provides a vehicle. Figure 4 is a schematic diagram of a vehicle structure provided by an embodiment of the present invention, with reference to Figure 4 The vehicle includes a battery 101, a controller 102 and an electromagnetic brake 103; the electromagnetic brake 103 includes a coil 1031; the controller 102 includes a switch unit 1021 and a control unit 1022; The first end of the coil 1031 is connected to the battery 101, the first end of the switch unit 1021 is connected to the second end of the coil 1031, and the second end of the switch unit 1021 is connected to the first power supply voltage; the control unit 1022 is connected to the control end of the switch unit 1021; the control unit 1022 is used to execute the vehicle control method provided by any embodiment of the present invention.

[0075] The battery 101 may be a power battery of the vehicle. The electromagnetic brake 103 may control the braking of the vehicle. For example, when the target speed of the vehicle (or the target speed of the motor) is zero, the electromagnetic brake 103 brakes, thereby achieving automatic braking.

[0076] The controller 102 may be a controller of the whole vehicle, that is, a controller for controlling the motor of the vehicle. The controller 102 includes a switch unit 1021 and a control unit 1022, and the control unit 1022 may include a control chip. The switch unit 1021 may include a switch transistor, etc. The first end of the coil 1031 is connected to the battery 101, for example, to the positive electrode of the battery, and the second end of the switch unit 1021 is connected to the first power supply voltage, and the first power supply voltage may be a ground voltage. When the switch unit 1021 is turned on, the first end of the switch unit 1021 is connected to the second end of the switch unit 1021, so that the second end of the coil 1031 is grounded, and the coil 1031 is energized, the armature is attracted, and the armature is separated from the brake disc, and the electromagnetic brake 103 is in an attracted state, that is, in an unbraked state. When the switch unit 1021 is disconnected, the second end of the coil 1031 is suspended, and the coil 1031 loses power, so that the armature presses the brake disc, and the electromagnetic brake 103 is in a braking state. The control unit 1022 can control whether the switch unit 1021 is turned on, thereby controlling whether the coil 1031 is energized, and further controlling whether the electromagnetic brake 103 is braking.

[0077] Specifically, when the electromagnetic brake 103 is not braking, the control unit 1022 obtains the actual current of the coil 1031, and based on the proportional integral control strategy, outputs a control signal to the control end of the switch unit 1021 according to the actual current of the coil 1031 and the reference current, thereby controlling the conduction time of the switch unit 1021, thereby controlling the time when the second end of the coil 1031 is grounded, thereby controlling the average voltage of the coil 1031, and controlling the effective current of the coil 1031, so that the current of the coil 1031 changes to the reference current, and the current of the coil 1031 is close to or equal to the reference current. In this way, the current of the coil 1031 can be controlled in real time according to the actual current of the coil 1031 fed back, so that when the current of the coil 1031 is affected by the temperature or the battery voltage, the current of the coil 1031 can still remain stable, that is, the current of the coil 1031 is always close to or equal to the reference current, thereby ensuring that the coil 1031 can stably attract the armature, thereby ensuring the stable operation of the electromagnetic brake 103, and improving the stability of the electromagnetic brake 103.

[0078] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0079] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A vehicle control method, characterized in that: The vehicle comprises a battery, a controller and an electromagnetic brake; the electromagnetic brake comprises a coil; the controller comprises a switch unit and a control unit; a first end of the coil is connected to the battery, a first end of the switch unit is connected to a second end of the coil, and a second end of the switch unit is connected to a first power supply voltage; The control unit is connected to the control end of the switch unit; The method is performed by the control unit; The method comprises: When the electromagnetic brake is not braking, the actual current of the coil is obtained, and based on a proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current of the coil and a reference current, so as to control the voltage of the coil and the current of the coil; wherein the reference current is the rated current or the holding current of the electromagnetic brake, and the holding current is a preset proportion of the rated current, and the preset proportion is less than 100%.

2. The method according to claim 1, characterized in that When the electromagnetic brake is not braking, based on the proportional-integral control strategy, a control signal is output to the control end of the switch unit according to the actual current and the reference current of the coil, including: When the electromagnetic brake is released, based on a proportional-integral control strategy, a control signal is output to a control terminal of the switch unit according to the actual current of the coil and the rated current; After a first preset time, based on a proportional-integral control strategy, a control signal is output to the control terminal of the switch unit according to the actual current of the coil and the holding current.

3. The method according to claim 1, characterized in that Based on a proportional-integral control strategy, a control signal is output to a control terminal of the switch unit according to the actual current of the coil and the reference current, including: The product of the difference between the actual current and the reference current and the proportional coefficient is used as the proportional term of the proportional-integral control strategy; The product of the proportional term and the integral coefficient and the sum of the previous integral term of the proportional-integral control strategy are used as the current integral term of the proportional-integral control strategy; Taking the maximum output value and the minimum output value as limit values, the sum of the proportional term and the current integral term is used as the output value of the proportional-integral control strategy, and the control signal corresponding to the output value is output to the control end of the switch unit; wherein the control signal is a pulse width modulation signal, the duty cycle of the pulse width modulation signal corresponding to the maximum output value is 100%, and the duty cycle of the pulse width modulation signal corresponding to the minimum output value is 0.

4. The method according to any one of claims 1 to 3, characterized in that After outputting a control signal to the control terminal of the switch unit according to the actual current of the coil and the reference current based on the proportional-integral control strategy, the method further includes: When the controller determines that the vehicle fails or receives a failure signal, obtaining a first rotation speed of a motor of the vehicle; After a second preset time period, obtaining a second rotation speed of the motor; If the second rotation speed is in a direction different from the first rotation speed, the electromagnetic brake is controlled to perform braking.

5. The method according to claim 4, characterized in that The vehicle also includes a brake pedal; If the second speed is in a direction different from the first speed, controlling the electromagnetic brake to brake comprises: If the second speed is in a direction different from the first speed and no braking signal from the brake pedal is received after a third preset time period, the electromagnetic brake is controlled to brake.

6. The method according to claim 4, characterized in that The vehicle also includes a brake pedal; If the second speed is in a direction different from the first speed, controlling the electromagnetic brake to brake comprises: If the second speed is in a different direction from the first speed and a brake signal from the brake pedal is received within a third preset time period, acquiring a third speed of the motor at least twice after a fourth preset time period; If the absolute value of the third rotational speed is greater than the absolute value of the first rotational speed for a consecutive preset number of times, the electromagnetic brake is controlled to brake; wherein the preset number of times is greater than 1.

7. The method according to claim 1, characterized in that The vehicle also includes a brake pedal; After outputting a control signal to the control terminal of the switch unit according to the actual current of the coil and the reference current based on the proportional-integral control strategy, the method further includes: When the controller determines that the vehicle fails or receives a failure signal, obtaining a first rotation speed of a motor of the vehicle; If a brake signal from the brake pedal is received within a third preset time period, obtaining a third rotation speed of the motor at least twice after a fourth preset time period; If the absolute value of the third rotational speed is greater than the absolute value of the first rotational speed for a consecutive preset number of times, the electromagnetic brake is controlled to brake; wherein the preset number of times is greater than 1.

8. The method according to claim 4, characterized in that After controlling the electromagnetic brake to brake, the method further comprises: If the accelerator stroke of the vehicle is greater than a preset stroke, the electromagnetic brake is controlled to stop braking, and after the accelerator stroke is zero, the electromagnetic brake is controlled to brake; wherein the preset stroke is greater than 80% of the maximum stroke of the accelerator.

9. The method according to claim 4, characterized in that Controlling the electromagnetic brake to brake includes: A control signal with a zero duty cycle is output to the control terminal of the switch unit.

10. A vehicle, characterized in that: The vehicle comprises a battery, a controller and an electromagnetic brake; the electromagnetic brake comprises a coil; the controller comprises a switch unit and a control unit; The first end of the coil is connected to the battery, the first end of the switch unit is connected to the second end of the coil, and the second end of the switch unit is connected to a first power supply voltage; the control unit is connected to the control end of the switch unit; the control unit is used to execute the vehicle control method described in any one of claims 1-9.

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