A vehicle and its control method

Abstract

The present invention discloses a vehicle and its control method. The vehicle includes a battery, a controller, and an electromagnetic brake; the electromagnetic brake includes a coil; the controller includes a switching unit and a control unit; a first end of the coil is connected to the battery, a first end of the switching unit is connected to a second end of the coil, and a second end of the switching unit is connected to a first power supply voltage; the control unit is connected to a control end of the switching unit; the control method of the vehicle is executed by the control unit; the control method of the vehicle includes: when the electromagnetic brake is not braking, based on a proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the reference current of the coil to control the voltage of the coil and thus control the current of the coil; wherein, the reference current is the rated current or the holding current of the electromagnetic brake, the holding current is a preset percentage of the rated current, and the preset percentage is less than 100%. The technical solution of the present invention improves the stability of the electromagnetic brake.

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, road vehicles, etc. The vehicle includes an electromagnetic brake, which can replace the traditional handbrake. The electromagnetic brake is electronically controlled and has the characteristics of no driver intervention and fast response speed. Therefore, it is favored by more and more vehicle manufacturers.

[0003] The electromagnetic brake includes a coil. After the coil is energized, it attracts the armature (i.e., the brake pad) to separate from the brake disc, so that the drive shaft of the vehicle can operate normally without braking. After the coil is de-energized, it no longer attracts the armature, so that the armature presses against the brake disc to realize vehicle braking.

[0004] The power battery of the vehicle can supply power to the coil. Whether the coil is energized and the voltage magnitude of the coil are controlled by the vehicle controller. However, the coil is an inductive load. When the electromagnetic brake works, the temperature rises, which causes the internal resistance of the coil to change with the temperature, and then causes the current of the coil to fluctuate greatly, affecting the magnetic force for attracting the armature, resulting in poor stability of the electromagnetic brake. Moreover, the battery voltage may change with the vehicle load, making the voltage at both ends of the coil unstable, which also affects the magnetic force for attracting the armature, resulting in poor stability of the electromagnetic brake. Summary of the Invention

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

[0006] According to one aspect of the present invention, a control method of a vehicle is provided. 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; the method is executed by the control unit;

[0007] The method includes:

[0008] When the electromagnetic brake is not braking, obtain the actual current of the coil, 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 and the reference current of the coil to control the voltage of the coil and thus control the current of the coil; wherein, the reference current is the rated current or the holding current of the electromagnetic brake, the holding current is a preset ratio of the rated current, and the preset ratio is less than 100%.

[0009] Optionally, when the electromagnetic brake is not braking, based on a proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the reference current of the coil, including:

[0010] When the electromagnetic brake releases braking, based on a proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the rated current of the coil;

[0011] After a first preset duration, based on a proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the holding current of the coil.

[0012] Optionally, based on a proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the reference current of the coil, including:

[0013] Taking the product of the difference between the actual current and the reference current and the proportionality coefficient as the proportional term of the proportional-integral control strategy;

[0014] Taking the sum of the product of the proportional term and the integral coefficient and the previous integral term of the proportional-integral control strategy as the current integral term of the proportional-integral control strategy;

[0015] Taking the sum of the proportional term and the current integral term as the output value of the proportional-integral control strategy with the maximum output value and the minimum output value as limits, and outputting the control signal corresponding to the output value to the control end of the switching 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.

[0016] Optionally, after outputting a control signal to the control end of the switching unit according to the actual current and the reference current of the coil based on a proportional-integral control strategy, it further includes:

[0017] When the controller determines that the vehicle has a fault or receives a fault signal, obtaining a first rotational speed of the motor of the vehicle;

[0018] After a second preset duration, obtaining a second rotational speed of the motor;

[0019] If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake.

[0020] Optionally, the vehicle further includes a brake pedal;

[0021] If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake includes:

[0022] If the direction of the second rotational speed is different from that of the first rotational speed, and no braking signal of the brake pedal is received after a third preset time period, control the electromagnetic brake to brake.

[0023] Optionally, the vehicle further includes a brake pedal;

[0024] If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake includes:

[0025] If the direction of the second rotational speed is different from that of the first rotational speed, and a braking signal of the brake pedal is received within a third preset time period, obtain the third rotational speed of the motor at least twice after a fourth preset time period;

[0026] If the absolute values of the third rotational speed for a continuous preset number of times are all greater than the absolute value of the first rotational speed, control the electromagnetic brake to brake; wherein, the preset number is greater than 1.

[0027] Optionally, the vehicle further includes a brake pedal;

[0028] After outputting a control signal to the control end of the switching unit according to the actual current and the reference current of the coil based on a proportional-integral control strategy, further includes:

[0029] When the controller determines that the vehicle has a fault or receives a fault signal, obtain the first rotational speed of the motor of the vehicle;

[0030] If a braking signal of the brake pedal is received within a third preset time period, obtain the third rotational speed of the motor at least twice after a fourth preset time period;

[0031] If the absolute values of the third rotational speed for a continuous preset number of times are all greater than the absolute value of the first rotational speed, control the electromagnetic brake to brake; wherein, the preset number is greater than 1.

[0032] Optionally, after controlling the electromagnetic brake to brake, further includes:

[0033] If the travel of the accelerator of the vehicle is greater than a preset travel, control the electromagnetic brake to stop braking, and after the travel of the accelerator is zero, control the electromagnetic brake to brake; wherein, the preset travel is greater than 80% of the maximum travel of the accelerator.

[0034] Optionally, controlling the electromagnetic brake to brake includes:

[0035] Output a control signal with a zero duty cycle to the control terminal of the switching unit.

[0036] According to another aspect of the present invention, a vehicle is provided, which includes a battery, a controller, and an electromagnetic brake; the electromagnetic brake includes a coil; the controller includes a switching unit and a control unit;

[0037] The first end of the coil is connected to the battery, the first end of the switching unit is connected to the second end of the coil, and the second end of the switching unit is connected to a first power supply voltage; the control unit is connected to the control terminal of the switching unit; the control unit is configured to execute the vehicle control method according to any embodiment of the present invention.

[0038] In the technical solution of the embodiment of the present invention, when the electromagnetic brake is not braking, the actual current of the coil is acquired, and based on the proportional-integral control strategy, a control signal is output to the control terminal of the switching unit according to the actual current and the reference current of the coil, thereby controlling the conduction duration of the switching unit, and further controlling the duration of the second end of the coil grounded, and then controlling the voltage of the coil, so that the current of the coil changes towards the reference current, and the current of the coil approaches or is equal to the reference current. In this way, the current of the coil can be controlled in real time according to the feedback of the actual current of the coil. Therefore, when the current of the coil is affected by temperature or battery voltage, the current of the coil can still be kept 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, and further ensuring the stable operation of the electromagnetic brake and improving the stability of the electromagnetic brake.

[0039] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

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

[0041] Figure 1 It is a flowchart of a vehicle control method provided by an embodiment of the present invention;

[0042] Figure 2 It is a flowchart of another vehicle control method provided by an embodiment of the present invention;

[0043] Figure 3 It is a flowchart of yet another vehicle control method provided by an embodiment of the present invention;

[0044] Figure 4 It is a schematic structural diagram of a vehicle provided by an embodiment of the present invention. Detailed implementation manners

[0045] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0047] An embodiment of the present invention provides a control method for a vehicle. 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; the control method of the vehicle is executed by the control unit. Among them, the vehicle can be a new energy vehicle, such as an electric vehicle, the vehicle can be an industrial vehicle, and industrial vehicles include forklifts and loaders, etc. It can also be a road vehicle. The battery can be the power battery of the vehicle. The electromagnetic brake can control the braking of the vehicle. For example, when the target speed of the vehicle (or the target rotation speed of the motor) is zero, the electromagnetic brake brakes, thereby realizing automatic braking.

[0048] The controller can be the controller for the whole vehicle, that is, the controller for controlling the motor of the vehicle. The controller includes a switching unit and a control unit. The control unit can include a control chip, such as a single-chip microcomputer chip or a digital processing chip, etc. The switching unit can include switching transistors, etc. The first end of the coil is connected to the battery, for example, connected to the positive electrode of the battery. The second end of the switching unit is connected to a first power supply voltage. The first power supply voltage can be a ground voltage. When the switching unit is turned on, the first end of the switching unit is connected to the second end of the switching unit, so that the second end of the coil is grounded, and the coil is energized to attract the armature, so that the armature is separated from the brake disc, and the electromagnetic brake is in the attracted state, that is, in the non-braking state. When the switching unit is turned off, the second end of the coil is suspended, the coil is de-energized, and no longer attracts the armature, so that the armature presses against the brake disc, and the electromagnetic brake is in the braking state. The control unit can control whether the switching unit is turned on, so as to control whether the coil is energized, and further control whether the electromagnetic brake brakes. In some other embodiments, the first end of the coil can also be connected to the negative electrode of the battery, and the first power supply voltage is a positive voltage. This embodiment is not limited.

[0049] Figure 1 It is a flowchart of a control method for a vehicle provided by an embodiment of the present invention. Refer to Figure 1 , the control method for the vehicle includes:

[0050] S110. When the electromagnetic brake is not braking, obtain the actual current of the coil.

[0051] Specifically, when the electromagnetic brake is not braking, that is, when the coil in the electromagnetic brake is energized to attract the armature 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, etc.

[0052] S120. Based on the proportional-integral control strategy, output a control signal to the control end of the switching unit according to the actual current and the reference current of the coil to control the voltage of the coil and thus control 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 percentage of the rated current, and the preset percentage is less than 100%.

[0053] 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 through linear combination of 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, the digital quantity corresponding to the duty cycle of the PWM signal being 100% is , and the digital quantity corresponding to the duty cycle of the PWM signal being 0 is 0. The duty cycle can be subdivided to achieve more precise control of the conduction duration of the switching unit, and thus more precise control of the voltage of the coil. In some other embodiments, the digital quantity can also adopt other formats, which are not limited in this embodiment. For example, the digital quantity can also adopt the Q48 format, that is, the digital quantity corresponding to the duty cycle of the PWM signal being 100% is , which is not limited in this embodiment.

[0054] Specifically, the output value of the proportional-integral control strategy can be adjusted through the actual current and the reference current, so as to adjust the control signal output to the control end of the switching unit, and then control the conduction duration of the switching unit, so as to control the duration of the second end of the coil grounded, and then control the average voltage of the coil, control the effective current of the coil, so that the current of the coil changes towards the reference current, and the current of the coil approaches or is equal to the reference current.

[0055] By setting the reference current to the rated current or the holding current, the coil can be controlled to have different currents according to the braking requirements. For example, when it is required that the electromagnetic brake attracts better, that is, when it is required that the coil attracts the armature better, the reference current can be set to the rated current, so that the magnetic force of the coil is larger, and the armature can be attracted better, ensuring that the drive shaft of the vehicle can operate normally and avoiding the situation of intermittent attraction due to insufficient magnetic force. When the armature is attracted stably or the power consumption needs to be reduced, the reference current can be set to the holding current, and the holding current is smaller, which can reduce the power consumption while ensuring stable attraction.

[0056] In the technical solution of this embodiment, when the electromagnetic brake is not braking, the actual current of the coil is obtained. Based on the proportional-integral control strategy, a control signal is output to the control terminal of the switching unit according to the actual current and the reference current of the coil, thereby controlling the conduction duration of the switching unit, and further controlling the duration of the second end of the coil being grounded, and further controlling the voltage of the coil, so that the current of the coil changes towards the reference current, and the current of the coil approaches or is equal to the reference current. In this way, the current of the coil can be controlled in real time according to the feedback of the actual current of the coil. Therefore, when the current of the coil is affected by 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, and further ensuring the stable operation of the electromagnetic brake and improving the stability of the electromagnetic brake.

[0057] Based on the above technical solution, optionally, when the electromagnetic brake is not braking, a control signal is output to the control terminal of the switching unit according to the actual current and the reference current of the coil based on the proportional-integral control strategy, including:

[0058] Step a1: When the electromagnetic brake is released from braking, a control signal is output to the control terminal of the switching unit based on the proportional-integral control strategy according to the actual current and the rated current of the coil.

[0059] Specifically, when starting to attract (i.e., just releasing the brake), 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 switching unit, and further controlling the voltage of the coil, and further controlling the current of the coil, so that the current of the coil approaches or is equal to the rated current. This makes the magnetic force of the coil larger, better attracting the armature, ensuring that the drive shaft of the vehicle can operate normally, and avoiding the situation of intermittent attraction due to insufficient magnetic force.

[0060] Step a2: After the first preset duration, a control signal is output to the control terminal of the switching unit based on the proportional-integral control strategy according to the actual current and the holding current of the coil.

[0061] Specifically, after the braking is released and stabilized, that is, after the armature is stably attracted, the reference current can be set to 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 switching unit, and further controlling the voltage of the coil, and further controlling the current of the coil, so that the current of the coil approaches or is equal to the holding current. The holding current is small, which can reduce the power consumption while ensuring stable attraction.

[0062] Based on the above technical solution, Figure 2 is a flowchart of another vehicle control method provided by an embodiment of the present invention. Optionally, referring to Figure 2 , the vehicle control method includes:

[0063] S210. When the electromagnetic brake is not braking, obtain the actual current of the coil.

[0064] S220. Take the product of the difference between the actual current and the reference current and the proportionality coefficient as the proportional term of the proportional-integral control strategy.

[0065] Wherein, the difference between the actual current and the reference current is the difference obtained by subtracting the actual current from the reference current.

[0066] Specifically, by calculating the difference between the actual current and the reference current, the deviation between the actual current and the reference current of the coil can be determined. According to the deviation between the actual current and the reference current of the coil, the output value of the proportional-integral control strategy is adjusted, thereby adjusting the output signal corresponding to the output value, so that the current of the coil can approach or be equal to the reference current.

[0067] Exemplarily, for example, the reference current is , the actual current is , the proportionality coefficient is , the proportional term is , then the proportional term is .

[0068] S230. Take the sum of the product of the proportional term and the integral coefficient and the previous integral term of the proportional-integral control strategy as the current integral term of the proportional-integral control strategy.

[0069] Specifically, the previous integral term of the proportional-integral control strategy is the integral term in the previous calculation period of the proportional-integral control strategy, and the current integral term of the proportional-integral control strategy is the integral term in the current calculation period. Wherein, the process of the proportional-integral control strategy outputting an output value according to the input values (actual current and reference current) is one calculation period. By determining the current integral term, the cumulative deviation between the actual current and the reference current can be determined. According to the cumulative deviation, the output value of the proportional-integral control strategy is adjusted, so that the current of the coil is closer to the reference current.

[0070] Exemplarily, 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.

[0071] S240. Taking the maximum output value and the minimum output value as limits, 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 switching unit to control the voltage of the coil and thus control the current of the coil. Wherein, the control signal is a pulse-width modulation signal, the duty ratio of the pulse-width modulation signal corresponding to the maximum output value is 100%, and the duty ratio of the pulse-width modulation signal corresponding to the minimum output value is 0.

[0072] Specifically, taking the maximum output value and the minimum output value as limits, 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, it is specified that the output value of the proportional-integral control strategy is 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 duration of the switching unit can be controlled, thereby controlling the duration of the second end of the coil being grounded, and further controlling the average voltage of the coil, so that the current of the coil changes towards the reference current, and the current of the coil approaches or is equal to the reference current.

[0073] Exemplarily, for example, the output value of the proportional-integral control strategy is , then the output value of the proportional-integral control strategy .

[0074] It can be known that after the vehicle is started and when the electromagnetic brake is not braked, the controller can cyclically obtain the actual current of the coil and continuously execute the proportional-integral control strategy in a loop, 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 and the reference current of the coil, so that the current of the coil approaches or is equal to the reference current.

[0075] In this way, the closed-loop regulation of the coil current is realized through the proportional-integral control strategy. When the actual current of the coil is greater than the reference current, the control unit will decrease the output value of the proportional-integral control strategy, so that the duty ratio of the control signal output to the control end of the switching unit decreases, reducing the average voltage of the coil and further reducing the effective current of the coil. 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 ratio of the control signal output to the control end of the switching unit increases, increasing the average voltage of the coil and further increasing the effective current of the coil. Thus, no matter how the inductance or impedance of the coil changes and how the battery voltage fluctuates, the current of the coil can be maintained stable, the magnetic force generated by the coil can be stable, the suction state of the electromagnetic brake can be stable, and the stability of the electromagnetic brake is improved.

[0076] 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, referring to Figure 3 , the vehicle control method includes:

[0077] S310. When the electromagnetic brake is not braking, obtain the actual current of the coil.

[0078] S320. Based on the proportional-integral control strategy, output a control signal to the control terminal of the switching unit according to the actual current and the reference current of the coil to control the voltage of the coil and thus control 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 percentage of the rated current, and the preset percentage is less than 100%.

[0079] S330. When the controller determines that the vehicle has a fault or receives a fault signal, obtain the first rotational speed of the motor of the vehicle.

[0080] Specifically, the vehicle having a fault can be that the rotational speed of the motor cannot be controlled, or the accelerator malfunctions, etc. The controller can judge whether the vehicle has a fault to determine whether the vehicle has a fault, or can also receive a fault signal from other devices (such as the central controller of the vehicle, etc.). When the controller determines that the vehicle has a fault or receives a fault signal, obtaining the first rotational speed of the motor of the vehicle can determine the first rotational speed of the motor when the vehicle has a fault.

[0081] S340. After a second preset time period, obtain the second rotational speed of the motor.

[0082] S350. If the direction of the second rotational speed is different from that of the first rotational speed, control the electromagnetic brake to brake.

[0083] Specifically, if the direction of the second rotational speed is different from that of the first rotational speed, it may be that after the vehicle has a fault, it changes from an uphill state to a downhill state, causing the direction of the rotational speed to change, then control the electromagnetic brake to brake and force the vehicle to stop to avoid the vehicle from slipping. It can avoid the problem that some vehicles do not have a brake pedal and the electromagnetic brake cannot brake when the target rotational speed of the motor is not zero.

[0084] Thus, when the vehicle is traveling on a slope, if 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 rotational speed of the motor will become faster and faster. By controlling the electromagnetic brake to brake, the problem that the target rotational speed of the motor is not zero and the electromagnetic brake cannot automatically brake in the related art can be avoided.

[0085] Based on the above technical solution, in some embodiments, optionally, the vehicle further includes a brake pedal; the brake pedal can be braked by the driver stepping on it.

[0086] If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake includes:

[0087] If the direction of the second rotational speed is different from that of the first rotational speed, and no braking signal of the brake pedal is received after a third preset time period, then control the electromagnetic brake to brake.

[0088] Specifically, if the direction of the second rotational speed is different from that of the first rotational speed, and no braking signal of the brake pedal is received after a third preset time period, that is, after the rotational 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 brake to prevent the vehicle from rolling backward. By setting the third preset time period, time is reserved for the driver to step on the brake pedal, which can avoid misjudgment.

[0089] Optionally, if the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake includes:

[0090] Step b1: If the direction of the second rotational speed is different from that of the first rotational speed, and a braking signal of the brake pedal is received within a third preset time period, then obtain the third rotational speed of the motor at least twice after a fourth preset time period.

[0091] Specifically, if the direction of the second rotational speed is different from that of the first rotational speed, and a braking signal of the brake pedal is received within a third preset time period, that is, after the rotational speed direction of the vehicle changes, the driver steps on the brake pedal in time, then obtain the third rotational speed of the motor at least twice after a fourth preset time period. The third rotational speed of the motor can be obtained at least twice continuously, or a preset interval time period can be set between two acquisitions of the third rotational speed. This embodiment does not make a limitation.

[0092] Step b2: If the absolute values of the third rotational speeds for a continuous preset number of times are all greater than the absolute value of the first rotational speed, then control the electromagnetic brake to brake; where the preset number is greater than 1.

[0093] Specifically, if the absolute values of the third rotational speeds for a continuous preset number of times are all greater than the absolute value of the first rotational speed, then after stepping on the brake pedal, if the absolute value of the motor rotational speed is still increasing, it is determined that the brake pedal fails and braking cannot be performed, then control the electromagnetic brake to brake. If there is no continuous preset number of times where the absolute values of the third rotational speeds are all greater than the absolute value of the first rotational speed, then control the electromagnetic brake not to brake, that is, the electromagnetic brake is in the attracted state.

[0094] Exemplarily, for example, the preset number is 2. After obtaining the third rotational speed for the first time, the relationship between the third rotational speed and the first rotational speed can be judged. If the absolute value of the third rotational speed obtained for the first time is greater than the absolute value of the first rotational speed, the error value is incremented by one; after obtaining the third rotational speed for the second time, if the absolute value of the third rotational speed obtained for the second time is greater than the absolute value of the first rotational speed, the error value is incremented by one. When the error value reaches the preset number, that is, the absolute values of the third rotational speeds for consecutive preset numbers are all greater than the absolute value of the first rotational speed, the electromagnetic brake is controlled to brake. If the absolute value of the third rotational speed obtained for the second time is less than or equal to the absolute value of the first rotational speed, the error value is zero, and the counting starts over until the error value reaches the preset number, and then the electromagnetic brake is controlled to brake. If among the third rotational speeds collected multiple times, there is no case where the absolute values of the third rotational speeds for consecutive preset numbers are all greater than the absolute value of the first rotational speed, the electromagnetic brake is controlled not to brake.

[0095] Optionally, after outputting a control signal to the control terminal of the switching unit according to the actual current and the reference current of the coil based on the proportional-integral control strategy, it further includes:

[0096] Step c1: When the controller determines that the vehicle has a fault or receives a fault signal, obtain the first rotational speed of the motor of the vehicle.

[0097] Step c2: If a braking signal of the brake pedal is received within the third preset duration, obtain the third rotational speed of the motor at least twice after the fourth preset duration.

[0098] Specifically, regardless of whether the direction of the motor rotational speed changes, if a braking signal of the brake pedal is received within the third preset duration, the third rotational speed of the motor can be obtained at least twice after the fourth preset duration. The third rotational speed of the motor can be obtained continuously at least twice, or there can be a preset interval duration between the two acquisitions of the third rotational speed, which is not limited in this embodiment.

[0099] Step c3: If the absolute values of the third rotational speeds for consecutive preset numbers are all greater than the absolute value of the first rotational speed, control the electromagnetic brake to brake; where the preset number is greater than 1.

[0100] Specifically, if the absolute values of the third rotational speeds for consecutive preset numbers are all greater than the absolute value of the first rotational speed, and after the brake pedal is depressed, the absolute value of the motor rotational speed is still increasing, it is determined that the brake pedal has a fault and braking cannot be performed, then control the electromagnetic brake to brake; if there is no case where the absolute values of the third rotational speeds for consecutive preset numbers are all greater than the absolute value of the first rotational speed, control the electromagnetic brake not to brake, that is, the electromagnetic brake is in the attracted state.

[0101] Optionally, after controlling the electromagnetic brake to brake, it further includes:

[0102] If the travel of the accelerator of the vehicle is greater than a preset travel, control the electromagnetic brake to stop braking, and after the travel of the accelerator is zero, control the electromagnetic brake to brake; wherein, the preset travel is greater than 80% of the maximum travel of the accelerator.

[0103] Specifically, after the vehicle breaks down and the electromagnetic brake brakes, if the travel of the accelerator of the vehicle is greater than the preset travel, 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, so that the vehicle can run normally. In this way, it is possible to avoid the problem that the vehicle cannot move after braking, resulting in the vehicle parking and obstructing traffic.

[0104] By setting the preset travel, when the travel of the accelerator of the vehicle is greater than the preset travel, the electromagnetic brake will be controlled to stop braking, which can avoid misjudgment and prevent the problem that the electromagnetic brake repeatedly attracts and releases due to the driver's frequent foot shaking.

[0105] Optionally, controlling the electromagnetic brake to brake includes:

[0106] Output a control signal with a zero duty cycle to the control end of the switch unit.

[0107] 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 zero duty cycle to the control end of the switch unit. The switch unit disconnects, and the second end of the coil is floating, that is, not grounded, so that the coil loses power and no longer attracts the armature, and the armature presses against the brake disc to realize the braking of the electromagnetic brake.

[0108] An embodiment of the present invention also provides a vehicle. Figure 4 It is a schematic structural diagram of a vehicle provided by an embodiment of the present invention. Refer 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;

[0109] 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 a 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 implementation scheme of the present invention.

[0110] Among them, the battery 101 can be the power battery of the vehicle. The electromagnetic brake 103 can control the braking of the vehicle. For example, when the target speed (or the target rotational speed of the motor) of the vehicle is zero, the electromagnetic brake 103 brakes, so as to realize automatic braking.

[0111] The controller 102 can be the controller for the whole vehicle, that is, the 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 can include a control chip. The switch unit 1021 can include a switching transistor, etc. The first end of the coil 1031 is connected to the battery 101, for example, connected to the positive pole of the battery. The second end of the switch unit 1021 is connected to a first power supply voltage, and the first power supply voltage can 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 then the coil 1031 is energized to attract the armature, so that the armature is separated from the brake disc, and the electromagnetic brake 103 is in the attracted state, that is, in the non-braking state. When the switch unit 1021 is turned off, the second end of the coil 1031 is floating, the coil 1031 loses power, so that the armature presses against the brake disc, and the electromagnetic brake 103 is in the braking state. The control unit 1022 can control whether the switch unit 1021 is turned on, so as to control whether the coil 1031 is energized, and further control whether the electromagnetic brake 103 brakes.

[0112] Specifically, when the electromagnetic brake 103 is not braking, the control unit 1022 acquires 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 and the reference current of the coil 1031, and further controls the conduction duration of the switch unit 1021, so as to control the duration of the second end of the coil 1031 being grounded, and further control the average voltage of the coil 1031, control the effective current of the coil 1031, so that the current of the coil 1031 changes towards the reference current, and the current of the coil 1031 approaches or is equal to the reference current. In this way, the current of the coil 1031 can be controlled in real time according to the feedback of the actual current of the coil 1031. Thus, when the current of the coil 1031 is affected by temperature or battery voltage, the current of the coil 1031 can still be kept stable, that is, the current of the coil 1031 is always close to or equal to the reference current, so as to ensure that the coil 1031 can stably attract the armature, and further ensure the stable operation of the electromagnetic brake 103 and improve the stability of the electromagnetic brake 103.

[0113] It should be understood that various forms of processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0114] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for a vehicle, characterized in that, The vehicle includes a battery, a controller, and an electromagnetic brake; the electromagnetic brake includes a coil; the controller includes a switching unit and a control unit; a first end of the coil is connected to the battery, a first end of the switching unit is connected to a second end of the coil, and a second end of the switching unit is connected to a first power supply voltage; The control unit is connected to a control end of the switching unit; The method is executed by the control unit; The method includes: When the electromagnetic brake is not braking, obtaining an actual current of the coil, and based on a proportional-integral control strategy, outputting a control signal to the control end of the switching unit according to the actual current and a reference current of the coil to control a voltage of the coil so as to control a current of the coil; wherein, the reference current is a rated current or a holding current of the electromagnetic brake, the holding current is a preset ratio of the rated current, and the preset ratio is less than 100%; After outputting the control signal to the control end of the switching unit according to the actual current and the reference current of the coil based on the proportional-integral control strategy, further included is: When the controller determines that the vehicle has a fault or receives a fault signal, obtaining a first rotational speed of a motor of the vehicle; After a second preset time period, obtaining a second rotational speed of the motor; If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake; The vehicle further includes a brake pedal; If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake, including: If the direction of the second rotational speed is different from that of the first rotational speed, and a braking signal of the brake pedal is received within a third preset time period, obtaining at least twice a third rotational speed of the motor after a fourth preset time period; If absolute values of the third rotational speed in a continuous preset number of times are all greater than an absolute value of the first rotational speed, controlling the electromagnetic brake to brake; wherein, the preset number is greater than 1; Or, after outputting the control signal to the control end of the switching unit according to the actual current and the reference current of the coil based on the proportional-integral control strategy, further included is: When the controller determines that the vehicle has a fault or receives a fault signal, obtaining a first rotational speed of a motor of the vehicle; If a braking signal of the brake pedal is received within a third preset time period, obtaining at least twice a third rotational speed of the motor after a fourth preset time period; If absolute values of the third rotational speed in a continuous preset number of times are all greater than an absolute value of the first rotational speed, controlling the electromagnetic brake to brake.

2. The method according to claim 1, wherein When the electromagnetic brake is not braking, outputting the control signal to the control end of the switching unit based on the proportional-integral control strategy according to the actual current and the reference current of the coil, includes: When the electromagnetic brake releases braking, outputting the control signal to the control end of the switching unit based on the proportional-integral control strategy according to the actual current and the rated current of the coil; After a first preset time period, outputting the control signal to the control end of the switching unit based on the proportional-integral control strategy according to the actual current and the holding current of the coil.

3. The method according to claim 1, wherein Based on the proportional-integral control strategy, a control signal is output to the control end of the switching unit according to the actual current and the reference current of the coil, including: Taking the product of the difference between the actual current and the reference current and the proportionality coefficient as the proportional term of the proportional-integral control strategy; Taking the sum of the product of the proportional term and the integral coefficient and the previous integral term of the proportional-integral control strategy as the current integral term of the proportional-integral control strategy; Taking the sum of the proportional term and the current integral term as the output value of the proportional-integral control strategy with the maximum output value and the minimum output value as limits, and outputting the control signal corresponding to the output value to the control end of the switching 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 claim 1, characterized in that If the direction of the second rotational speed is different from that of the first rotational speed, controlling the electromagnetic brake to brake, including: If the direction of the second rotational speed is different from that of the first rotational speed and no braking signal of the brake pedal is received after a third preset time period, controlling the electromagnetic brake to brake.

5. The method according to claim 1, wherein After controlling the electromagnetic brake to brake, it further includes: If the travel of the accelerator of the vehicle is greater than a preset travel, controlling the electromagnetic brake to stop braking, and after the travel of the accelerator is zero, controlling the electromagnetic brake to brake; wherein, the preset travel is greater than 80% of the maximum travel of the accelerator.

6. The method according to claim 1, characterized in that, Controlling the electromagnetic brake to brake, including: Outputting a control signal with a duty cycle of zero to the control end of the switching unit.

7. A vehicle, characterized in that, The vehicle includes a battery, a controller and an electromagnetic brake; the electromagnetic brake includes a coil; the controller includes a switching unit and a control unit; The first end of the coil is connected to the battery, the first end of the switching unit is connected to the second end of the coil, the second end of the switching unit is connected to a first power supply voltage; the control unit is connected to the control end of the switching unit; the control unit is used to execute the vehicle control method according to any one of claims 1-6.

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