A current sampling-based electromagnetic valve current control method for a vehicle body stability system

Abstract

The application discloses a kind of based on current sampling car body stabilizing system solenoid current control method, it is related to automobile chassis brake system control technical field, including current sampling and processing module, solenoid resistance model module and current closed-loop control module, current sampling and processing module gathers actual high-frequency current sampling value in a PWM control period, the average of current sampling value is calculated, to realize current closed-loop control;And the average of current sampling value square is calculated, solenoid resistance model module calculates heat output according to the average of current sampling value square, and heat conduction is calculated in combination with ambient temperature, and the iterative calculation of actual coil resistance is given;Current closed-loop control module is based on actual coil resistance and the average of current sampling value, and the duty cycle of solenoid valve driving signal is calculated according to target current.The PWM control technology of the application realizes solenoid valve current control, to realize the continuous linear control of solenoid valve pressure, and the effect of optimizing noise problem.

Description

Technical Field

[0001] This invention relates to the field of automotive chassis braking system control technology, and in particular to a method for controlling the current of an electromagnetic valve in a vehicle stability system based on current sampling. Background Technology

[0002] like Figure 1 As shown, the Electronic Stability Control (ESC) system consists of a controller 1, a valve block 2, and a motor 3. The valve block has two oil inlets 4, each connected to one of the two chambers of the master cylinder, and four oil outlets 5, each connected to one of the four wheel cylinders. The main working principle of ESC is to determine vehicle stability based on driver input (brake pedal, steering wheel angle) and sensor signals (master cylinder pressure, wheel speed, acceleration, yaw rate). When the vehicle is close to instability, ESC controls the solenoid valves and DC brushed motor within the valve block to independently control the hydraulic pressure of the four wheels' brakes, maintaining vehicle stability. Therefore, the control of the solenoid valves is a crucial component of ESC.

[0003] Generally, ESC (Electronic Stability Control) requires wheel cylinder pressure control to quickly and accurately track the target wheel cylinder pressure. Traditional solenoid valve control technology is an on / off control technology, which uses the energization or de-energization of an electromagnetic coil to open or close the solenoid valve, thereby achieving a stepped change in wheel cylinder pressure. This control method means that the target wheel cylinder pressure can only be discrete rather than continuous, and the noise caused by the solenoid valve switching also affects comfort.

[0004] To address the aforementioned problems, this invention presents a current control method for the solenoid valve of a vehicle stability system based on current sampling. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a current sampling-based electromagnetic valve current control method for vehicle stability systems. Based on PWM electromagnetic coil control, this method enables continuous variation of the control current, allowing the electromagnetic valve opening to change continuously. This results in higher precision linear wheel cylinder pressure control, and the NVH characteristics of ESC are also greatly optimized due to the elimination of electromagnetic valve opening and closing noise.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A current control method for a solenoid valve in a vehicle stability system based on current sampling includes a current sampling and processing module, an electromagnetic coil resistance model module, and a current closed-loop control module.

[0008] The control method includes:

[0009] The current sampling and processing module collects the actual high-frequency current sampling value within one PWM control cycle and calculates the average value of the current sampling value to achieve current closed-loop control.

[0010] Furthermore, the average value of the squares of the current sampling values ​​is calculated. The electromagnetic coil resistance model module calculates the heat generation based on the average value of the squares of the current sampling values, and calculates the heat conduction in combination with the ambient temperature, providing an iterative calculation of the actual coil resistance.

[0011] The current closed-loop control module calculates the duty cycle of the solenoid valve drive signal based on the average value of the actual coil resistance and the current sample value, according to the target current.

[0012] The calculated duty cycle is used to control the solenoid valve hardware circuit.

[0013] Furthermore, the hardware circuit includes a power supply, a PWM switch, a current sensor, and an electromagnetic coil, wherein the electromagnetic coil includes a resistor and an inductor.

[0014] The power supply, PWM switch, electromagnetic coil, and current sensor are connected in series and then grounded. One end of the power supply is connected to the PWM switch, and the other end of the PWM switch is connected to the electromagnetic coil and the current sensor in sequence and then back to the power supply. One end of the resistor is connected to the PWM switch, and the other end is connected to the electromagnetic coil. The other end of the electromagnetic coil is connected to the current sensor.

[0015] Furthermore, PWM signals are used for drive control. By periodically turning the PWM switch on and off, different equivalent voltages are achieved according to different on times. By controlling the equivalent voltage, the current of the solenoid coil on the solenoid valve is continuously changed.

[0016] Furthermore, within one PWM control cycle, assuming the electromagnetic coil resistance R remains constant, closed-loop tracking control of the target current is achieved by tracking the target current with the average current.

[0017] Furthermore, the average value of the actual current samples is calculated as follows:

[0018]

[0019] The average of the squares of the actual current sample values ​​is calculated as follows:

[0020]

[0021] The average value of the actual current sampled value and the average value of the square of the actual current sampled value are calculated using the above calculation method.

[0022] Furthermore, the iterative calculation formula for the actual electromagnetic coil resistance is as follows:

[0023]

[0024] Furthermore, the control method for the hardware circuit adopts a combination of feedforward control and proportional-integral feedback control:

[0025] Feedforward control and proportional-integral feedback control calculate the PWM duty cycle respectively, and the combined calculation results control the output PWM duty cycle command, which is then executed by the hardware.

[0026] Furthermore, the formula for calculating the PWM duty cycle by the feedforward control is as follows:

[0027]

[0028] The formula for calculating the PWM duty cycle by the proportional-integral feedback control is as follows:

[0029]

[0030] The final output duty cycle is calculated using a combination of feedforward control and proportional-integral feedback control: λ(k) = λ ff (k)+λ fb (k).

[0031] Furthermore, the hardware circuit also includes a freewheeling diode, which is connected in parallel with the electromagnetic coil and the current sensor.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention introduces a current sensor and realizes the control of the solenoid valve current through PWM control technology. That is, based on PWM solenoid coil control, the control current is continuously changed, so that the opening degree of the solenoid valve can be continuously changed, thereby achieving a higher precision linear cylinder pressure control effect. Moreover, since there is no noise from the opening and closing of the solenoid valve, the NVH characteristics of ESC can also be greatly optimized. In general, the discretization of solenoid valve pressure control and noise problems of automotive ESC system are solved. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the vehicle stability system structure of the present invention;

[0034] Figure 2 This is the electromagnetic washer control circuit in this invention;

[0035] Figure 3 This is a schematic diagram of the electromagnetic coil current control principle in this invention;

[0036] Figure 4 The current waveform diagram for one PWM control cycle.

[0037] Reference numerals: 1. Controller; 2. Valve block; 3. Motor; 4. Oil inlet; 5. Oil outlet. Detailed Implementation

[0038] The technical methods 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 some embodiments of the present invention, and not all embodiments.

[0039] This invention discloses a current control method for an electromagnetic valve in a vehicle stability system based on current sampling. The working principle is as follows: based on high-frequency actual coil current sampling, the actual coil resistance is calculated. The closed-loop control module calculates the duty cycle of the driving PWM based on the target current, actual resistance, and actual current, so as to drive the actual hardware circuit.

[0040] It comprises the following components: hardware circuitry and software modules.

[0041] like Figure 2 As shown, the hardware circuit includes a power supply (voltage Ub), a PWM switch, a freewheeling diode, a current sensor (sampling value I), and an electromagnetic coil. The electromagnetic coil includes a resistor R and an inductor L. The power supply voltage Ub and the current sensor are used to acquire the actual high-frequency current sampling value I.

[0042] The power supply, PWM switch, electromagnetic coil, and current sensor are connected in series and grounded. One end of the power supply is connected to the PWM switch, and the other end of the PWM switch is connected to the electromagnetic coil and current sensor in sequence, then back to the power supply. One end of a resistor is connected to the PWM switch, and the other end is connected to the electromagnetic coil. The other end of the electromagnetic coil is connected to the current sensor. The electromagnetic coil is driven by PWM to achieve high-frequency switching of the power supply voltage.

[0043] The hardware circuit also includes a freewheeling diode, which is connected in parallel with the electromagnetic coil and the current sensor. When used with the freewheeling diode, the current can change more smoothly, avoiding voltage surges.

[0044] like Figure 3 As shown, the software module consists of three parts: current sampling and processing module, electromagnetic coil resistance model module, and current closed-loop control module.

[0045] In summary, the control method of this invention is as follows: First, the current sampling and processing module collects the actual high-frequency current sampling value within a PWM control cycle and calculates the average value of the current sampling value to achieve current closed-loop control; then, the average value of the square of the current sampling value is calculated, and the electromagnetic coil resistance model module calculates the heat generation based on the average value of the square of the current sampling value and calculates the heat conduction in combination with the ambient temperature, giving an iterative calculation of the actual coil resistance; next, the current closed-loop control module calculates the duty cycle of the solenoid valve drive signal based on the actual coil resistance and the average value of the current sampling value, according to the target current; finally, the calculated duty cycle is used to control the solenoid valve hardware circuit.

[0046] The method for controlling the current of the solenoid valve proposed in this invention will be described in detail below with specific embodiments.

[0047] For linear pressure control of a solenoid valve, the ideal target current I Tar (t) is smooth and continuous.

[0048] At a given moment, the voltage-current relationship of the electromagnetic coil is:

[0049]

[0050] Where U is the control voltage, I is the actual current of the electromagnetic coil, R is the resistance of the electromagnetic coil at the current moment, and L is the inductance of the electromagnetic coil.

[0051] It can be seen that the electromagnetic coil current is changed by controlling the voltage U. In order to achieve arbitrary voltage U driving, this application uses PWM technology. By periodically turning the control switch on and off, different equivalent voltages are achieved according to different on times. Equivalent voltage = PWM duty cycle * power supply voltage. That is, the voltage is adjusted by adjusting the PWM duty cycle, thereby achieving continuous control of the current.

[0052] The electromagnetic coil is driven by a PWM switch to achieve high-frequency switching of the power supply voltage. The current waveform across the electromagnetic coil is a triangular shape, as shown in the diagram. Figure 4 As shown, the actual coil current change within one PWM control cycle T is shaped like a triangular wave. The rise and fall times depend on the PWM duty cycle λ. Assuming the electromagnetic coil resistance R remains constant within one PWM control cycle, the average electromagnetic coil current is:

[0053]

[0054] To achieve the target current I Tar (t) In terms of closed-loop tracking control, what needs to be achieved is the average current I. meanTracking of the target current. In other words, current closed-loop control is achieved by tracking the target current with the average current.

[0055] Another factor that cannot be ignored is the change in the electromagnetic coil resistance R during the control process. This change is mainly affected by the control current I(t) and the ambient temperature E, and its dynamic equation is:

[0056]

[0057] Where k h k is the coefficient of heat generation. c R is the thermal conductivity coefficient. E This is the standard resistance value of the electromagnetic coil at ambient temperature E.

[0058] Considering a PWM cycle, assuming the resistance R of the electromagnetic coil remains constant, the rate of change of resistance is determined by the average of the squares of the electromagnetic coil current:

[0059]

[0060]

[0061] Based on the above analysis, the various modules of the software module can be designed. First, the current sampling and processing module samples the actual coil current I(i) at a period Ts = T / n (n>=10), where i = 1, 2, ..., n. Then, for the k-th PWM time period, it calculates the average value of the sampled current and the average value of the square of the sampled current.

[0062]

[0063]

[0064] Secondly, the coil resistance model module iteratively calculates the actual resistance of the electromagnetic coil based on the average of the squares of the current samples:

[0065]

[0066] Finally, the current closed-loop control module calculates the drive duty cycle based on the average value of the target current and the actual current.

[0067] The duty cycle output consists of a control output composed of feedforward control and a feedback control. The calculation results of the two are superimposed to form a duty cycle command, specifically:

[0068] The control method that combines feedforward control and feedback control is as follows:

[0069] λ(k)=λ ff (k)+λ fb (k)

[0070] The feedforward part is:

[0071]

[0072] The feedback section uses a proportional-integral (PI) controller.

[0073]

[0074] Where k p and k i These are the proportional coefficient and the integral coefficient, respectively.

[0075] Feedforward control and proportional-integral feedback control are the two components that make up the PWM duty cycle. The calculation results of the two are superimposed to form a duty cycle command, which is executed by hardware. The advantage of feedforward control is its fast response, while the advantage of proportional-integral feedback control is its simple and intuitive controller structure, ease of understanding, and ease of parameter adjustment. By combining feedforward control and proportional-integral feedback control to output the duty cycle, precise control of the electromagnetic coil is achieved.

[0076] By controlling the output PWM duty cycle, the voltage can be regulated and controlled, thereby achieving continuous change of current. Continuous current control can achieve continuous change of solenoid valve opening, thereby achieving continuous control of brake fluid flow. Ultimately, the change of wheel cylinder pressure is also continuous.

[0077] The specific implementation principle of this invention is as follows: The current sampling and processing module processes the high-frequency current sampling values ​​within a PWM cycle, calculating both the average value and the average squared value of the sampling values. The former is used for current closed-loop control, and the latter for coil resistance calculation. The coil resistance model calculates the heat generation based on the average squared value of the current sampling values ​​and combines this with the ambient temperature to calculate heat conduction, thus providing an iterative calculation of the actual resistance. The current closed-loop control module calculates the PWM duty cycle based on the actual coil resistance and the average current sampling values, according to the target current. The controller consists of a feedforward controller and a feedback controller. The feedforward controller is designed based on the voltage-current dynamic equation of the coil, and the feedback controller is a proportional-integral controller. The control output is the PWM duty cycle, used to drive the actual hardware circuit.

[0078] This invention meets the ESC system's requirement for continuous control of solenoid valve current. It adopts a current closed-loop control method, which uses sampling feedback to correct the control. This avoids control target deviations caused by external interference or model parameter deviations. By utilizing PWM technology, the entire invention's technical solution achieves continuous and precise control of wheel cylinder pressure and significantly reduces operating noise.

[0079] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical methods and inventive concepts of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the current of a solenoid valve in a vehicle stability system based on current sampling, characterized in that, It includes a current sampling and processing module, an electromagnetic coil resistance model module, and a current closed-loop control module; The control method includes: The current sampling and processing module collects the actual high-frequency current sampling value within one PWM control cycle and calculates the average value of the current sampling value to achieve current closed-loop control. Furthermore, the average value of the squares of the current sampling values ​​is calculated. The electromagnetic coil resistance model module calculates the heat generation based on the average value of the squares of the current sampling values, and calculates the heat conduction in combination with the ambient temperature, providing an iterative calculation of the actual electromagnetic coil resistance. The current closed-loop control module calculates the duty cycle of the solenoid valve drive signal based on the average value of the actual electromagnetic coil resistance and the current sample value, according to the target current. The calculated duty cycle is used to control the hardware circuit of the solenoid valve; The average value of the actual current samples is calculated as follows: in, is the actual coil current in the i-th time period, and n is the time period count; The average of the squares of the actual current sample values ​​is calculated as follows: The average value of the actual current sampled values ​​and the average value of the square of the actual current sampled values ​​are calculated using the above calculation method. The iterative calculation formula for the actual electromagnetic coil resistance is as follows: in, This represents the actual resistance of the electromagnetic coil in the previous time period. For time period, The coefficient of heat generation. The thermal conductivity coefficient, This is the standard resistance value of the coil at ambient temperature E; The control method for the hardware circuit is achieved by combining feedforward control and proportional-integral feedback control: Feedforward control and proportional-integral feedback control calculate the PWM duty cycle respectively, and the results of the two calculations are combined to control the output PWM duty cycle command, which is then executed by the hardware. The formula for calculating the PWM duty cycle by the feedforward control is as follows: in, The target current value for the current time period. The target current value for the previous time period. For coil inductance, To control the voltage; The formula for calculating the PWM duty cycle by the proportional-integral feedback control is as follows: Among them, This is the proportionality coefficient. The integral coefficient; The final output duty cycle is calculated using a combination of feedforward control and proportional-integral feedback control. .

2. The method for controlling the current of a solenoid valve in a vehicle stability system based on current sampling according to claim 1, characterized in that, The hardware circuit includes a power supply, a PWM switch, a current sensor, and an electromagnetic coil, wherein the electromagnetic coil includes a resistor and an inductor. The power supply, PWM switch, electromagnetic coil, and current sensor are connected in series and then grounded. One end of the power supply is connected to the PWM switch, and the other end of the PWM switch is connected to the electromagnetic coil and the current sensor in sequence and then back to the power supply. One end of the resistor is connected to the PWM switch, and the other end is connected to the electromagnetic coil. The other end of the electromagnetic coil is connected to the current sensor.

3. The method for controlling the current of a solenoid valve in a vehicle stability system based on current sampling according to claim 2, characterized in that, The drive control is achieved by using a PWM signal. By periodically turning the PWM switch on and off, different equivalent voltages are achieved according to different on-times. By controlling the equivalent voltage, the current of the solenoid coil on the solenoid valve is continuously changed.

4. The method for controlling the current of a solenoid valve in a vehicle stability system based on current sampling according to claim 2, characterized in that, Within one PWM control cycle, assuming the electromagnetic coil resistance R remains constant, closed-loop tracking control of the target current is achieved by tracking the target current with the average current.

5. The method for controlling the current of a solenoid valve in a vehicle stability system based on current sampling according to claim 2, characterized in that, The hardware circuit also includes a freewheeling diode, which is connected in parallel with the electromagnetic coil and the current sensor.

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