Hybrid braking system and control method for an electric mine dump truck driverless system

Abstract

The application relates to the technical field of brake control of vehicles and discloses a hybrid brake system and a control method of an unmanned system of an electric mine dump truck. The hybrid brake system comprises EBS (electronically controlled brake system) control and motor torque control, and through the joint action of the two, the final control effect is achieved. The EBS control corresponds to mechanical braking, and the motor torque control corresponds to regenerative braking. When the unmanned system issues a brake request, the above two types of control strategy design can meet the requirements of safety and smoothness.

Description

Technical Field

[0001] This invention relates to the field of vehicle braking control technology, and in particular to a hybrid braking system and control method for an unmanned driving system of an electric mining dump truck. Background Technology

[0002] With the introduction of the national new energy strategy, electric vehicles powered by power batteries are increasingly becoming an important direction for the development of the automotive industry, and the importance of the research and application of electric vehicle technology is becoming increasingly prominent. At present, most of the mining dump trucks used in open-pit mines are powered by diesel engines. These vehicles have the following defects: (1) They emit harmful gases, causing great air pollution; (2) They consume a lot of fuel, resulting in high vehicle operating costs; (3) When braking, most of the vehicle's kinetic energy is converted into heat energy and dissipated, resulting in energy waste; (4) They all use mechanical braking, which reduces the service life of braking system components and increases vehicle operating costs and safety hazards.

[0003] Compared to traditional mechanical braking, hybrid braking offers significant advantages in improving vehicle energy efficiency, increasing electric vehicle range, and reducing environmental pollution. In electric vehicles or hybrid electric vehicles, regenerative braking improves energy efficiency. However, during electric braking, the braking torque is limited by factors such as battery state and motor speed. When conditions such as excessive battery SOC (State of Charge), low vehicle speed, activation of ABS (Anti-lock Braking System), or motor drive system malfunction occur, regenerative braking must be stopped. Abruptly disengaging at these times would cause drastic changes in braking force, leading to sudden changes in vehicle deceleration and reduced comfort. Therefore, to ensure vehicle safety and smooth driving, hybrid braking systems and their corresponding distribution control strategies are crucial.

[0004] Chinese invention patent CN112549977B proposes a method and system for controlling energy recovery on downhill slopes in a pure electric mining truck, aiming to solve the technical problem that existing energy recovery methods for pure electric mining trucks cannot meet the energy recovery requirements under slopes of 15% to 50%. However, in this invention patent, information such as vehicle speed, motor braking torque, and recoverable energy during downhill driving is calculated based on currently known parameters and formulas, resulting in a significant deviation between the desired outcome and the actual effect, thus limiting its practicality.

[0005] Chinese invention patent CN110614921A discloses a braking energy recovery system and control method for electric commercial vehicles. The disclosed technical solution comprehensively considers the coordinated control method of pneumatic braking and electric braking in electric vehicles under normal braking conditions, resulting in a more rational distribution of braking force. However, the rear brake controller can only control one axle. In most cases, wide-body vehicles typically use two axles at the rear, which may lead to deviations in the control strategy's distribution of braking force. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a hybrid braking system and control method for an unmanned driving system of an electric mining dump truck. The hybrid braking system comprises EBS (Electrically Controlled Brake System) control and motor torque control, which work together to achieve the final control effect. EBS control corresponds to mechanical braking, while motor torque control corresponds to regenerative braking. When the unmanned driving system issues a braking request, the above two control strategies are designed to achieve both safety and smoothness requirements.

[0007] The specific technical solution of the present invention is as follows:

[0008] A hybrid braking system for an unmanned driving system of an electric mining dump truck includes a mechanical braking subsystem and a regenerative braking subsystem;

[0009] The mechanical braking subsystem includes a master brake valve, an EBS controller, a single-channel bridge control module, a dual-channel bridge control module, an air supply unit, wheel speed sensors, and wheel brakes.

[0010] The brake master valve is connected to the EBS controller and the air supply unit respectively. The EBS controller controls the wheel brake through a single-channel bridge control module and a dual-channel bridge control module.

[0011] The regenerative braking subsystem includes a motor controller and a motor;

[0012] The motor controller is connected to the battery and the motor, and the motor is connected to the transmission system.

[0013] Preferably, the air supply unit includes an air compressor, an air handling unit, and an air storage tank connected in sequence.

[0014] A control method for a hybrid braking system based on the unmanned driving system of the electric mining dump truck includes the following steps:

[0015] Step 1: The front-end main control unit calculates the target braking opening in real time;

[0016] Step 2: Obtain the desired deceleration based on the target braking opening;

[0017] Step 3: Determine if the remaining capacity of the power battery, braking intensity, and vehicle speed are within a reasonable range; if they are within a reasonable range, proceed to Step 4; if they are not within a reasonable range, proceed to Step 6.

[0018] Step 4: Determine if the desired deceleration is greater than the maximum allowable deceleration of the motor; if the desired deceleration is not greater than the maximum allowable deceleration of the motor, send a request for the desired regenerative braking torque to the VCU; if the desired deceleration is greater than the maximum allowable deceleration of the motor, send a request for the maximum allowable regenerative braking torque of the motor to the VCU, and proceed to Step 6.

[0019] Step 5: In the initial stage of regenerative braking, the VCU sends a deceleration request to the EBS controller and exits at the preset time; In the final stage of regenerative braking: when the vehicle speed drops to the preset value, the VCU sends a deceleration request to the EBS controller until the vehicle stops.

[0020] Step 6: The VCU sends a request for the desired deceleration of mechanical braking to the EBS controller;

[0021] Step 7: Return to Step 1.

[0022] Preferably, the hybrid braking strategy of the control method is as follows:

[0023] (1) Let T e_allowed To the maximum allowable feedback torque of the VCU, T e_allowed Converted to braking deceleration a e_allowed :

[0024]

[0025] Among them, i g For the gearbox ratio, i o The main reduction ratio is given by η, the overall mechanical efficiency is given by 0.9, m is the total mass of the vehicle, and r is the total mass of the vehicle. w The static radius of the wheel;

[0026] If T e_allowed =0, then regenerative braking is not activated;

[0027] (2) If T e_allowed If the value is greater than 0, regenerative braking will be activated;

[0028] If a q ≤a e_allowed Then the desired regenerative braking torque T is sent to the VCU. q :

[0029]

[0030] If a q >ae_allowed Then, the maximum allowable feedback torque T is sent to the VCU. e_allowed ;

[0031] After sending a regenerative braking request to the VCU, the actual regenerative braking torque T of the motor is... a It is not equal to the expected regenerative braking torque;

[0032] (3) Mechanical braking:

[0033] Based on the desired deceleration a q and the actual regenerative braking torque T fed back by the VCU a Calculate the control quantities for mechanical braking:

[0034] like The deceleration required for mechanical braking is

[0035] like but

[0036] a) Within t0 after issuing the regenerative braking request, the VCU requests a deceleration from the EBS controller. q ; in the subsequent t l Within this timeframe, the requested deceleration decreases exponentially to zero until the EBS controller braking intervention is completely disengaged.

[0037] b) In the case of regenerative braking only, when the vehicle speed drops below V0, the VCU sends a deceleration of a to the EBS. q Upon receiving a braking request, the system implements closed-loop deceleration control until the vehicle stops or braking ends.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The hybrid braking system and control method proposed in this invention based on the unmanned driving system of the electric mining dump truck improves the braking control performance and longitudinal control accuracy of the whole vehicle by optimizing the system design and control strategy, while meeting the requirements of the unmanned driving system for the brake control of the drive-by-wire chassis, thereby improving the driving safety and scene adaptability of the electric mining dump truck.

[0040] (2) The hybrid braking system and control method proposed in this invention based on the unmanned driving system of the electric mining dump truck combine motor regenerative braking and mechanical braking. Under the premise of ensuring the overall braking demand, it makes full use of the regenerative braking generated by the motor to improve the driving range of the electric mining dump truck. At the same time, it has a significant improvement in longitudinal control effect compared with the traditional braking strategy.

[0041] (3) The hybrid braking system and control method proposed in this invention based on the electric mining dump truck unmanned driving system effectively allocates the theoretically calculated target deceleration to mechanical braking and electric braking by combining the upper-level control strategy with the lower-level braking system, thereby reducing unnecessary braking behavior and improving the transportation efficiency of the unmanned driving system. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the accompanying drawings. The accompanying drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the hybrid braking system of the unmanned driving system for electric mining dump trucks of the present invention.

[0044] Figure 2 This is a flowchart of the hybrid braking system control method for the unmanned driving system of the electric mining dump truck of the present invention.

[0045] Figure 3 This is a state machine logic diagram illustrating the hybrid braking system of the unmanned driving system for electric mining dump trucks of the present invention. Detailed Implementation

[0046] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0048] The hybrid braking system and control method for the unmanned driving system of electric mining dump trucks proposed in this invention send commands through the upper-level hybrid braking system control strategy to drive the hybrid braking system to perform braking behavior, thereby achieving reasonable control of the target deceleration of the electric mining dump truck. The overall design concept is as follows:

[0049] Based on the braking characteristics of electric mining dump trucks, the motor participates in energy recovery in real time according to the energy recovery strategy when decelerating or stopping. Under different working conditions, electric braking (i.e. regenerative braking) and mechanical braking are required to act alone or in combination.

[0050] The target braking deceleration or target braking opening is requested in the following manner:

[0051] (1) Send a corresponding torque request to the regenerative braking subsystem;

[0052] (2) Send the corresponding deceleration request to the mechanical braking subsystem.

[0053] a) Desired deceleration: Based on the braking opening calculated in real time by the front-end main control unit, the desired deceleration is obtained through the corresponding relationship.

[0054] b) Based on the real-time feedback torque from the regenerative braking subsystem, the equivalent torque to the wheel ends is calculated using the gearbox ratio, final drive ratio, and overall mechanical efficiency of the transmission. Then, based on the known total vehicle mass and wheel static radius, the equivalent braking deceleration is finally derived.

[0055] like Figure 1 As shown, the hybrid braking system of the unmanned driving system for electric mining dump trucks includes a mechanical braking subsystem and a regenerative braking subsystem.

[0056] The mechanical braking subsystem includes a master brake valve, an EBS controller, a single-channel bridge control module, a dual-channel bridge control module, an air supply unit, wheel speed sensors, and wheel brakes.

[0057] The brake master valve is connected to the EBS controller and the air supply unit, and the EBS controller controls the wheel brake through a single-channel bridge control module and a dual-channel bridge control module.

[0058] The air supply unit includes an air compressor, an air handling unit, and an air storage tank connected in sequence.

[0059] The regenerative braking subsystem includes a motor controller and a motor.

[0060] The motor controller is connected to both the battery and the motor, and the motor is connected to the transmission system.

[0061] The working principle of the mechanical braking subsystem is as follows: The EBS controller receives the pedal travel signal transmitted by the brake master valve or the deceleration command transmitted by the ADS controller and the vehicle control unit (VCU). After internal ECU calculation and processing, the braking pressure is distributed and output to the single-channel bridge control module and the dual-channel bridge control module respectively, and then output to the wheel brakes to implement braking.

[0062] The regenerative braking subsystem operates as follows: the motor is switched to generator operation, utilizing the inertia of the mining dump truck to drive the motor rotor to rotate, thereby generating a reversing torque. This converts a portion of the kinetic or potential energy into electrical energy, which is then stored or utilized; thus, it is an energy recovery process. The motor controller feeds back the maximum allowable braking torque of the motor to the VCU in real time. The VCU converts this maximum braking torque into braking deceleration and compares it with the target deceleration, thereby implementing different hybrid braking control strategies.

[0063] Based on the aforementioned hybrid braking system, the hybrid braking strategy is formulated as follows:

[0064] (1) If the maximum regenerative torque allowed by the VCU is zero, the regenerative braking subsystem will not be activated.

[0065] (2) If the maximum allowable regenerative torque of the VCU is greater than zero, the regenerative braking subsystem is activated. Further, if the desired deceleration is less than or equal to the allowable deceleration of the motor, the desired regenerative braking torque is sent to the VCU. If the desired deceleration is greater than the allowable deceleration of the motor, the maximum allowable motor braking torque is sent to the VCU.

[0066] (3) Mechanical braking: Calculate the control quantity required for mechanical braking based on the target braking deceleration request and the actual regenerative braking torque fed back by the VCU.

[0067] Example 1

[0068] A hybrid braking system control method for an unmanned driving system of an electric mining dump truck, such as... Figure 2 As shown, it includes the following steps:

[0069] Step 1: The front-end main control unit calculates the target braking opening in real time.

[0070] Step 2: Obtain the desired deceleration based on the target braking opening.

[0071] Step 3: Determine whether the remaining capacity of the power battery, braking intensity, and vehicle speed are within a reasonable range; if they are within a reasonable range, proceed to Step 4; if they are not within a reasonable range, proceed to Step 6.

[0072] Step 4: Determine whether the desired deceleration is greater than the maximum allowable deceleration of the motor. If the desired deceleration is not greater than the maximum allowable deceleration of the motor, send a request for the desired regenerative braking torque to the VCU. If the desired deceleration is greater than the maximum allowable deceleration of the motor, send a request for the maximum allowable regenerative braking torque of the motor to the VCU and proceed to Step 6.

[0073] Step 5: In the initial stage of regenerative braking, the VCU sends a deceleration request to the EBS controller and exits at the preset time. In the final stage of regenerative braking, when the vehicle speed drops to the preset value, the VCU sends a deceleration request to the EBS controller until the vehicle stops.

[0074] Step 6: The VCU sends a request for the desired deceleration of mechanical braking to the EBS controller.

[0075] Step 7: Return to Step 1.

[0076] The hybrid braking strategy in the above control method is executed as follows:

[0077] (1) Let T e_allowed (T e_allowed ≥0) is the maximum allowable feedback torque of the VCU, and T e_allowed Converted to braking deceleration a e_allowed :

[0078]

[0079] Among them, i g For the gearbox ratio, i o The main reduction ratio is given by η, the overall mechanical efficiency is given by 0.9, m is the total mass of the vehicle, and r is the total mass of the vehicle. w Let be the static radius of the wheel.

[0080] If T e_allowed =0, then regenerative braking is not activated.

[0081] (2) If T e_allowed If the value is greater than 0, regenerative braking is activated.

[0082] If a q ≤a e_allowed Then the desired regenerative braking torque T is sent to the VCU. q :

[0083]

[0084] If a q >a e_allowed Then, the maximum allowable feedback torque T is sent to the VCU. e_allowed .

[0085] After sending a regenerative braking request to the VCU, the actual regenerative braking torque T of the motor is... a It is not equal to the expected regenerative braking torque.

[0086] (3) Mechanical braking:

[0087] Based on the desired deceleration a q and the actual regenerative braking torque T fed back by the VCU a(When regenerative braking is not allowed, T) a =0) Calculate the control quantity of mechanical braking:

[0088] like The deceleration required for mechanical braking is (VCU sends to EBS controller)

[0089] like but

[0090] a) Within t0 after issuing the regenerative braking request, the VCU requests a deceleration from the EBS controller. q During the subsequent t1, the requested deceleration decreases exponentially to zero until the EBS controller braking intervention is completely disengaged.

[0091] b) In the case of regenerative braking only, when the vehicle speed drops below V0, the VCU sends a deceleration of a to the EBS. q Upon receiving a braking request, the system implements closed-loop deceleration control until the vehicle stops or braking ends.

[0092] In addition, the following is an explanation of the switching of the vehicle's service braking state:

[0093] The vehicle's service braking system should switch between the following five states based on its own condition and the external deceleration request: regenerative braking only, mechanical braking only, hybrid braking involving both regenerative and mechanical braking, no braking, and braking disengagement. The state switching logic is as follows: Figure 3 As shown in Table 1, the state switching conditions are as follows.

[0094] Table 1

[0095]

[0096]

[0097] Additional notes: The following prerequisites may also be set for the regenerative braking of the motor in this invention:

[0098] In autonomous driving mode, when the vehicle is in neutral (N) or reverse (R), only friction braking can be applied, and regenerative braking is ineffective. The distribution of regenerative braking force should also meet the following requirements: (1) Under the premise of ensuring braking stability and safety, regenerative braking should be selected as much as possible; (2) When the vehicle speed is too low, the SOC is too high, emergency braking is required, or the ABS function is activated, friction braking should be selected, and motor regenerative braking should be disengaged.

[0099] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0100] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0101] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a hybrid braking system based on an unmanned driving system for electric mining dump trucks, characterized in that, The hybrid braking system includes a mechanical braking subsystem and a regenerative braking subsystem; The mechanical braking subsystem includes a master brake valve, an EBS controller, a single-channel bridge control module, a dual-channel bridge control module, an air supply unit, wheel speed sensors, and wheel brakes. The brake master valve is connected to the EBS controller and the air supply unit respectively. The EBS controller controls the wheel brake through a single-channel bridge control module and a dual-channel bridge control module. The regenerative braking subsystem includes a motor controller and a motor; The motor controller is connected to the battery and the motor, and the motor is connected to the transmission system. The control method includes the following steps: Step 1: The front-end main control unit calculates the target braking opening in real time; Step 2: Obtain the desired deceleration based on the target braking opening; Step 3: Determine if the remaining capacity of the power battery, braking intensity, and vehicle speed are within a reasonable range; if they are within a reasonable range, proceed to Step 4; if they are not within a reasonable range, proceed to Step 6. Step 4: Determine if the desired deceleration is greater than the maximum allowable deceleration of the motor; if the desired deceleration is not greater than the maximum allowable deceleration of the motor, send a request for the desired regenerative braking torque to the VCU; if the desired deceleration is greater than the maximum allowable deceleration of the motor, send a request for the maximum allowable regenerative braking torque of the motor to the VCU, and proceed to Step 6. Step 5: In the initial stage of regenerative braking, the VCU sends a deceleration request to the EBS controller and exits at the preset time; In the final stage of regenerative braking: when the vehicle speed drops to the preset value, the VCU sends a deceleration request to the EBS controller until the vehicle stops. Step 6: The VCU sends a request for the desired deceleration of mechanical braking to the EBS controller; Step 7: Return to Step 1; The hybrid braking strategy of the control method is as follows: (1) Let For the maximum allowable feedback torque of the VCU, Converted to braking deceleration : in, For the gearbox speed ratio, Main reduction ratio, The overall mechanical efficiency is set to 0.

9. The total mass of the vehicle. The static radius of the wheel; like If so, regenerative braking will not be activated; (2) If Then regenerative braking will be activated; like Then the desired regenerative braking torque is sent to the VCU. : like Then, the maximum allowable feedback torque is sent to the VCU. ; After sending a regenerative braking request to the VCU, the actual regenerative braking torque of the motor It is not equal to the expected regenerative braking torque; (3) Mechanical braking: Based on the desired deceleration and the actual regenerative braking torque fed back by the VCU Calculate the control quantities for mechanical braking: like The deceleration required for mechanical braking is ; like ,but a) After issuing a regenerative braking request t Within 0, the deceleration requested by the VCU from the EBS controller is ; in the subsequent t Within 1 minute, the requested deceleration decreases to zero exponentially until the EBS controller braking intervention is completely disengaged. b) In the case of regenerative braking only, when the vehicle speed drops to V When the value is below 0, the VCU sends a deceleration value to the EBS. Upon receiving a braking request, the system implements closed-loop deceleration control until the vehicle stops or braking ends.

2. The control method according to claim 1, characterized in that, The air supply unit includes an air compressor, an air handling unit, and an air storage tank connected in sequence.

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