An electronic mechanical brake with a symmetrical double-screw structure and a control method thereof

Abstract

The present invention discloses an electronic mechanical brake with a symmetrical double-screw structure and a control method, belonging to the field of vehicle engineering technology. The electronic mechanical brake includes a braking mechanism comprising two screws, a front brake caliper body, and a rear brake caliper body. The screws are arranged in a front-to-back direction and are divided into two sections. The threads of the front and rear sections of the screws are in opposite directions and are respectively threadedly connected to a front nut and a rear nut. The two screws are capable of synchronous rotation. The front brake caliper body and the rear brake caliper body are respectively arranged on the front and rear sides of a brake disc, with the left and right sides of the front brake caliper body being fixed to the two front nuts, and the left and right sides of the rear brake caliper body being fixed to the two rear nuts, respectively. The two screws rotate synchronously, and the front brake caliper body and the rear brake caliper body move toward or away from each other with the front and rear nuts, respectively, to brake or release the brake disc. The present invention can solve the problem of wear on one-sided friction pads and has the advantages of stable operation, simplified structure, and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle engineering, and relates to a vehicle brake structure, in particular to an electronic mechanical brake with a symmetrical double-screw structure and a control method thereof. Background Art

[0002] The braking systems of traditional fuel-powered vehicles primarily utilize hydraulic braking technology. While this technology has become quite mature and highly reliable after years of development, it still has some shortcomings. For example, the hydraulic braking system is complex, involving numerous components and pipelines, which increases manufacturing and maintenance costs. Furthermore, hydraulic braking has a relatively slow response speed, and braking efficiency needs to be improved. More importantly, the use of brake fluid can cause environmental pollution, which does not meet current environmental protection requirements.

[0003] To overcome these shortcomings, brake-by-wire technology has garnered widespread attention and research in recent years. This technology replaces traditional mechanical and hydraulic connections with electronic signal transmission, eliminating brake fluid, boosters, and complex piping systems. This results in a simpler braking system and more flexible layout. Furthermore, the brake-by-wire system utilizes electrical energy as its power source, transmitting energy via wires and conveying braking commands via signal lines, enabling intelligent distribution of braking force. This not only improves braking response speed but also overall braking performance. However, practical applications of brake-by-wire technology still face challenges, such as wear on one side of the friction pad in the floating caliper disc structure and dimensional mismatch between the electromechanical brake and traditional hydraulic brake designs. Summary of the Invention

[0004] The present invention provides an electronic mechanical brake with a symmetrical double-screw structure and a control method thereof, so as to overcome the defects of the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides an electronic mechanical brake with a symmetrical double-screw structure for braking a brake disc, including a braking mechanism; the braking mechanism includes two screws, a front brake caliper body and a rear brake caliper body; the screws are arranged in the front and rear directions and are divided into two sections; the thread rotation directions of the front section screw and the rear section screw are opposite, and are respectively threadedly connected with a front nut and a rear nut; the two screws can rotate synchronously; the front brake caliper body and the rear brake caliper body are respectively arranged on the front and rear sides of the brake disc, and the left and right sides of the front brake caliper body are respectively fixed with the two front nuts, and the left and right sides of the rear brake caliper body are respectively fixed with the two rear nuts; when the two screws rotate synchronously, the front brake caliper body and the rear brake caliper body move toward each other with the front nut and the rear nut respectively, and when they move to clamp the brake disc, braking is achieved; when the two screws rotate synchronously in opposite directions, the front brake caliper body and the rear brake caliper body move oppositely with the front nut and the rear nut respectively, loosening the brake disc and releasing the brake.

[0007] Furthermore, it also includes a brake motor and a gear reduction mechanism; the brake motor drives the two lead screws to rotate synchronously; the brake motor drives the two lead screws to rotate synchronously after being decelerated by the gear reduction mechanism; the two lead screws have the same thread rotation direction and the same rotation direction.

[0008] Furthermore, the brake motor is arranged between the two lead screws, and the gear reduction mechanism is arranged at the front end of the brake motor; the gear reduction mechanism includes a mounting plate and a first-stage reduction assembly and a second-stage reduction assembly arranged on the front and rear sides of the mounting plate; the first-stage reduction assembly includes a first-stage driving gear and two first-stage driven gears, and the second-stage reduction assembly includes two second-stage driving gears and two second-stage driven gears; the two first-stage driven gears are both externally meshed with the first-stage driving gear; the brake motor drives the first-stage driving gear to rotate, and the two first-stage driven gears rotate synchronously therewith; the two first-stage driven gears and the two second-stage driving gears correspond one to one and are coaxially mounted on both sides of the mounting plate; the two second-stage driving gears rotate synchronously with their corresponding first-stage driven gears respectively; the two second-stage driven gears are externally meshed with the two second-stage driving gears and rotate synchronously with them; the front ends of the two lead screws are respectively fixed to the two second-stage driven gears and rotate synchronously with them; the electronic mechanical brake also includes a housing; the lead screw is mounted in the housing through a pair of deep groove ball bearings.

[0009] Furthermore, a parking lock mechanism is included; the parking lock mechanism can lock the rotor shaft of the brake motor.

[0010] Furthermore, the parking lock mechanism includes a spring electromagnet unit and a friction plate unit; the spring electromagnet unit is composed of an electromagnet and a spring; when power is applied, the electromagnetic force overcomes the spring force and the spring electromagnet unit shortens; when power is removed, the electromagnetic force disappears and the spring electromagnet unit extends under the action of the spring force; the friction plate unit includes a follower friction plate and a locking friction plate; the follower friction plate is fixed on the rotor shaft of the brake motor and rotates with the rotor shaft; the locking friction plate is fixed to the spring electromagnet unit and moves with the shortening and extension of the spring electromagnet unit; when the spring electromagnet unit is de-energized and extended, the locking friction plate moves toward the follower friction plate to press the follower friction plate, and the rotor shaft is locked; when the spring electromagnet unit is energized and shortened, the locking friction plate moves away from the follower friction plate, and the rotor shaft is unlocked.

[0011] Furthermore, the brake motor is arranged between two screws, and the parking lock mechanism is arranged on the rear side of the brake motor; the front brake caliper body is box-shaped, and the parking lock mechanism is located inside the front brake caliper body; the rear brake caliper body matches the front brake caliper body and is hoe-shaped.

[0012] Furthermore, brake friction pads are fixed on the side of the front brake caliper body and the rear brake caliper body facing the brake disc; a number of balls are provided between the screw and the front nut and the rear nut, that is, the screw, the two nuts (the front nut and the rear nut) and the balls respectively constitute two planetary ball screw motion conversion mechanisms.

[0013] In a second aspect, the present invention further provides a control method for the above-mentioned electronic mechanical brake with a symmetrical double-screw structure: when the front brake caliper body and the rear brake caliper body move toward each other and a brake gap exists between them and the brake disc, the brake motor control mode adopts a speed mode; when the front brake caliper body and the rear brake caliper body contact the brake disc and the brake gap between them is eliminated, the brake motor control mode adopts a torque mode;

[0014] The method for determining whether the brake clearance has been eliminated is as follows: calibrate the brake motor to obtain the brake clearance elimination time; if the braking time is less than the brake clearance elimination time, the front brake caliper body and the rear brake caliper body do not contact the brake disc; when the braking time is equal to the brake clearance elimination time, the brake clearance is eliminated.

[0015] Furthermore, the method for calibrating the brake motor to obtain the brake clearance elimination time is as follows: the brake pedal opening is stepped on to 100%, so that the front brake caliper body and the rear brake caliper body clamp the brake disc, and in the process, the precise contact probability of the front brake caliper body and the rear brake caliper body contacting the brake disc is calculated in real time based on fuzzy control. P 精确 , and get the exact contact probability P 精确 and corrected braking time t of P精确 - t curve; P 精确 - t The maximum value of the curve corresponds to the contact moment, and the corresponding correction braking time is t Time for eliminating brake clearance;

[0016] Among them, the precise contact probability is calculated based on fuzzy control P 精确 The method is as follows: the first input variable of fuzzy control is the angular velocity of the brake motor, the second input variable is the angular acceleration of the brake motor, and the output variable is the contact probability between the front brake caliper body and the rear brake caliper body and the brake disc; first, fuzzification is performed to divide the input variables and output variables into fuzzy sets and determine the corresponding Gaussian membership function; then, fuzzy reasoning is performed to eliminate the change characteristics of the angular velocity and angular acceleration of the brake motor according to the brake clearance, and multiple fuzzy rules are established to cover various situations in different stages of the braking process; then, the activation strength of the fuzzy rules is calculated and rule aggregation is performed; finally, the centroid method is used to perform defuzzification processing to obtain the accurate contact probability P 精确 .

[0017] Furthermore, the fuzzification method is:

[0018] The first input variable is the angular velocity of the brake motor. ω The domain of discourse is [0, ω max ], ω max is the maximum angular velocity of the brake motor; divide the domain into n ω angular velocity fuzzy sets ; Gaussian membership function of angular velocity fuzzy set for , where i ω is the number of the angular velocity fuzzy set, i ω =1~ n ω , for The central value of , for The standard deviation of , takes a fixed value;

[0019] The second input variable is the angular acceleration of the brake motor. β The domain of discourse is [- β 2, β 1], where - β 2 is the maximum angular deceleration when the brake motor decelerates,β 1 is the maximum angular acceleration when the brake motor accelerates; the domain is divided into n 1 forward acceleration fuzzy set , a zero acceleration fuzzy set ZE and n 2 negative deceleration fuzzy sets ; Gaussian membership function of forward accelerating fuzzy sets for , where is the number of the forward acceleration fuzzy set, =1~ n 1, for The central value of , for Standard deviation, fixed value; Gaussian membership function of zero acceleration fuzzy set for , where C ZE for The central value of C ZE =0, for The standard deviation of , takes a fixed value; Gaussian membership function of negative deceleration fuzzy set for , where is the number of the negative deceleration fuzzy set, =1~ n 2, for The central value of , for The standard deviation of , takes a fixed value;

[0020] Output variable contact probability P The domain of discourse is [0,1], which is divided evenly into n P contact probability fuzzy set ; Gaussian membership function of contact probability fuzzy set for , where is the number of the contact probability fuzzy set, for The central value of , for The standard deviation of , takes a fixed value.

[0021] Furthermore, in the fuzzy reasoning, H Fuzzy rules , including: the acceleration phase before the front brake caliper and the rear brake caliper contact the brake disc: the angular velocity of the brake motor ω for , brake motor angular acceleration β for , contact probability P for ; Uniform speed stage: Braking motor angular velocity ω for , brake motor angular acceleration β for ZE , contact probability P for CP 1; deceleration phase after the front and rear brake calipers come into contact with the brake disc: brake motor angular velocity ω for , brake motor angular acceleration β for , contact probability P for ; Abnormal working condition: Braking motor angular velocity ω for , brake motor angular acceleration β for , contact probability P for CP 1.

[0022] Furthermore, the method for calculating the activation strength of fuzzy rules and performing rule aggregation is:

[0023] No. i The activation strength of the fuzzy rules α i for:

[0024] ;

[0025] Where, i is the number of the fuzzy rule, i =1~ H , and They are i The corresponding angular velocity of the brake motor under the fuzzy rules ω and brake motor angular acceleration β Gaussian membership function of ;

[0026] For the activated fuzzy rules, the corresponding contact probability fuzzy sets are aggregated according to their activation strength, and the outputs of all fuzzy rules are superimposed. for:

[0027] ;

[0028] Where, For the i Activation intensity under fuzzy rules α i The weighted output variable Gaussian membership function, ;

[0029] The method for performing defuzzification processing is: P Divide into h Calculate the weighted sum to get P 精确 :

[0030] ;

[0031] Where, L is the contact probability P equal parts h The number of copies, L =0~ h , P L For the L Probability of contact in equal parts P .

[0032] The present invention provides an electromechanical brake with a symmetrical dual-screw structure, in which a single brake motor simultaneously drives two screws. These two screws, along with their front and rear nuts, collectively drive the movement of the brake pads on either side of the brake disc. Compared to conventional single-drive mechanisms, the use of dual screws reduces the force applied to a single screw, lowering the strength requirements required for screw selection and thus reducing manufacturing costs. Furthermore, by simultaneously driving the brake pads with dual screws, the present invention achieves more uniform wear of the brake pads, reduces the likelihood of uneven wear, and increases the service life of the brake pads. Furthermore, the dual-screw structure itself also serves as a guide for the movement of the brake pads, replacing the guide pins found in conventional disc brakes. Furthermore, the present invention features a gear reduction mechanism located at the outermost end of the brake, while the parking lock mechanism and brake motor are structurally integrated and located in the middle of the brake. The use of a specially configured brake caliper significantly improves the space utilization of the entire brake assembly, resulting in a streamlined structure and the potential for lightweighting the vehicle. The present invention also provides a control method for an electronic mechanical brake, which calculates the time it takes to eliminate the brake gap between the front brake caliper body, the rear brake caliper body and the brake disc based on fuzzy control, thereby accurately controlling the control mode of the brake motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the external structure of an electronic mechanical brake with a symmetrical double-screw structure;

[0034] Figure 2 This is a schematic diagram of the structure of an electronic mechanical brake with a symmetrical double-screw structure without the housing;

[0035] Figure 3 This is an exploded diagram of the structure of the electromechanical brake and brake disc with a symmetrical double-screw structure;

[0036] Figure 4 It is a structural diagram of the lead screw, front nut and rear nut in an electronic mechanical brake with a symmetrical double lead screw structure;

[0037] Figure 5 It is a structural diagram of the gear reduction mechanism in an electronic mechanical brake with a symmetrical double-screw structure;

[0038] Figure 6 It is a structural diagram of the parking lock mechanism in an electromechanical brake with a symmetrical double-screw structure;

[0039] Figure 7 It is a schematic structural diagram of the front brake caliper body in an electromechanical brake with a symmetrical double-screw structure;

[0040] Figure 8 It is a schematic structural diagram of the rear brake caliper body in an electromechanical brake with a symmetrical double-screw structure;

[0041] Figure 9 It is a flow chart of a control method of an electronic mechanical brake with a symmetrical double-screw structure;

[0042] Figure 10 This is a flow chart of a method for calibrating a brake motor to obtain the brake gap elimination time;

[0043] The marks in the accompanying drawings are: 1. Braking mechanism; 11. Screw; 111. Front nut; 112. Rear nut; 113. Deep groove ball bearing; 12. Front brake caliper body; 13. Rear brake caliper body; 14. Brake friction plate; 2. Brake motor; 21. Rotor shaft; 3. Gear reduction mechanism; 31. Mounting plate; 32. Primary reduction assembly; 321. Primary driving gear; 322. Primary driven gear; 33. Secondary reduction assembly; 331. Secondary driving gear; 332. Secondary driven gear; 4. Housing; 5. Parking lock mechanism; 51. Spring electromagnet unit; 521. Follower friction plate; 522. Locking friction plate; A. Brake disc. DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0045] like Figures 1 to 3 As shown, this embodiment provides an electromechanical brake with a symmetrical double-screw structure for braking a brake disc A, including a brake mechanism 1, a brake motor 2, a gear reduction mechanism 3, a housing 4 and a parking lock mechanism 5.

[0046] like Figures 2 to 4As shown, the brake mechanism 1 includes two lead screws 11, a front brake caliper body 12, and a rear brake caliper body 13. The lead screws 11 are arranged in the front-to-back direction and are divided into two sections. The threads of the front and rear lead screws have opposite rotation directions and are respectively threadedly connected to a front nut 111 and a rear nut 112. The two lead screws 11 are capable of rotating synchronously. The front brake caliper body 12 and the rear brake caliper body 13 are respectively arranged on the front and rear sides of the brake disc A. The left and right sides of the front brake caliper body 12 are respectively fixed to the two front nuts 111 of the two lead screws 11, and the left and right sides of the rear brake caliper body 13 are respectively fixed to the two rear nuts 112 of the two lead screws 11. Specifically, the front nuts 111 and the rear nuts 112 are each equipped with a flange and are fixed to the front brake caliper body 12 and the rear brake caliper body 13 via the flange. Preferably, a plurality of balls are provided between the lead screw 11 and the front nuts 111 and the rear nuts 112 to reduce friction.

[0047] When the two lead screws 11 rotate synchronously, the front brake caliper body 12 and the rear brake caliper body 13 move toward each other along with the front nut 111 and the rear nut 112, respectively. When they move to clamp the brake disc A, braking is achieved. When the two lead screws 11 rotate synchronously in the opposite direction, the front brake caliper body 12 and the rear brake caliper body 13 move in the opposite direction along with the front nut 111 and the rear nut 112, respectively, loosening the brake disc A and releasing the brake.

[0048] like Figures 2 to 4 As shown, the brake motor 2 drives the two lead screws 11 to rotate synchronously. Further, the brake motor 2 drives the two lead screws 11 to rotate synchronously after being decelerated by the gear reduction mechanism 3.

[0049] In a preferred embodiment, the two lead screws 11 have the same thread rotation direction and rotate in the same direction, thereby achieving synchronous rotation to drive the front brake caliper body 12 and the rear brake caliper body 13 to move toward or away from each other along with the front nut 111 and the rear nut 112. Of course, the above effect can also be achieved by configuring the two lead screws 11 to have opposite thread rotation directions and rotate in opposite directions.

[0050] Specifically, such as Figures 2 to 5As shown, the brake motor 2 is disposed between the two lead screws 11, and the gear reduction mechanism 3 is disposed at the front end of the brake motor 2. The gear reduction mechanism 3 includes a mounting plate 31 and a primary reduction assembly 32 and a secondary reduction assembly 33 disposed on the front and rear sides of the mounting plate 31. The primary reduction assembly 32 includes a primary driving gear 321 and two primary driven gears 322, and the secondary reduction assembly 33 includes two secondary driving gears 331 and two secondary driven gears 332. The two primary driven gears 322 are disposed on the left and right sides of the primary driving gear 321 and are externally meshed with the primary driving gear 321. The brake motor 2 drives the primary driving gear 321 to rotate, and the two primary driven gears 322 rotate synchronously therewith. The two primary driven gears 322 and the two secondary driving gears 331 correspond to each other and are coaxially mounted on the front and rear sides of the mounting plate 31 via rolling bearings. The two secondary driving gears 331 rotate synchronously with their corresponding primary driven gears 322. The two secondary driven gears 332 are arranged on the left and right sides of the two secondary driving gears 331 and respectively mesh with the two secondary driving gears 331 and rotate synchronously therewith. The front ends of the two lead screws 11 are respectively fixed to the two secondary driven gears 332 and rotate synchronously therewith.

[0051] like Figure 1 and Figure 3 As shown, the housing 4 is composed of multiple parts to facilitate installation. The brake mechanism 1, brake motor 2 and gear reduction mechanism 3 are all arranged in the housing 4. Among them, the mounting plate 31 is fixed in the housing 4. Figure 4 As shown, the screw 11 is mounted within the housing 4 via a pair of deep groove ball bearings 113. Due to the characteristics of the deep groove ball bearings 113, the screw 11 has a certain amount of axial positional float. This can be used to adjust the alignment of the brake mechanism 1 when the clearances between the brake disc A and the front and rear brake caliper bodies 12, 13 are unequal. Specifically, the pair of deep groove ball bearings 113 are disposed on the front and rear sides of the secondary driven gear 332, with the front deep groove ball bearing 113 mounted on the mounting plate 31.

[0052] like Figure 2 、 Figure 3 and Figure 6As shown, the parking lock mechanism 5 can lock the rotor shaft 21 of the brake motor 2. The parking lock mechanism 5 includes a spring electromagnet unit 51 and a friction plate unit. The spring electromagnet unit 51 is composed of an electromagnet and a spring. When power is applied, the electromagnetic force overcomes the spring force, the spring is compressed, and the spring electromagnet unit 51 shortens. When power is removed, the electromagnetic force disappears, and the spring electromagnet unit 51 extends under the action of the spring force. The spring electromagnet unit 51 is conventional, and its specific structure is not described in detail here. The friction plate unit includes a follower friction plate 521 and a locking friction plate 522. The follower friction plate 521 is fixed to the rotor shaft 21 of the brake motor 2 and rotates with the rotor shaft 21. The locking friction plate 522 is fixed to the spring electromagnet unit 51 and moves as the spring electromagnet unit 51 shortens and lengthens.

[0053] When the spring electromagnet unit 51 is de-energized and extends, the locking friction plate 522 moves toward the following friction plate 521 until it presses against the following friction plate 521, locking the rotor shaft 21. When the spring electromagnet unit 51 is energized and shortened, the locking friction plate 522 moves away from the following friction plate 521, unlocking the rotor shaft 21.

[0054] In a preferred embodiment, if Figure 2 、 Figure 3 、 Figures 6 to 8 As shown, the parking lock mechanism 5 is arranged on the rear side of the brake motor 2. The front brake caliper body 12 is box-shaped, and the parking lock mechanism 5 is located in the box-shaped space of the front brake caliper body 12. The rear brake caliper body 13 matches the front brake caliper body 12 and is hoe-shaped.

[0055] like Figure 2 As shown, brake friction pads 14 are fixed on the sides of the front brake caliper body 12 and the rear brake caliper body 13 facing the brake disc A.

[0056] The operating process of the symmetrical dual-screw electromechanical brake includes service braking, service brake release, parking brake, and parking brake release. Braking commands are issued by the vehicle's electronic control unit and responded to by brake motor 2 to achieve the above process.

[0057] The service braking process includes the following steps:

[0058] S1.1. Determine the braking demand based on the current vehicle driving state and brake pedal depth, generate a required braking force signal, and input it into the on-board electronic control unit for storage.

[0059] S1.2. The on-board electronic control unit sends a braking signal to brake motor 2.

[0060] S1.3. Brake motor 2 receives a signal from the vehicle's electronic control unit and rotates forward, driving screw 11 to rotate forward. Screw 11 then drives front brake caliper 12 and rear brake caliper 13 through front nut 111 and rear nut 112, respectively, to move, thereby moving brake pad 14 until brake pad 14 clamps brake disc A. During this period, if one brake pad 14 contacts brake disc A before the other, deep groove ball bearing 113 can provide axial floating capacity for screw 11 to adjust brake mechanism 1 for brake alignment, allowing the other brake pad 14 to quickly contact brake disc A.

[0061] The service brake release process includes the following steps:

[0062] S2.1. The vehicle-mounted electronic control unit sends a brake release signal to brake motor 2.

[0063] S2.2. The brake motor 2 receives a signal from the vehicle electronic control unit, and the brake motor 2 rotates in the opposite direction, driving the screw 11 to rotate in the opposite direction. The screw 11 drives the front brake caliper body 12 and the rear brake caliper body 13 to move through the front nut 111 and the rear nut 112 respectively, thereby driving the brake friction pad 14 to move away from the brake disc A, and making the rotor of the brake motor 2 reach the set position according to the set brake clearance.

[0064] The parking brake process includes the following steps:

[0065] S3.1. Detect vehicle motion information. When the vehicle stops, the driver operates the vehicle and shifts the vehicle into P gear. The onboard electronic control unit sends a parking signal to the brake.

[0066] S3.2. Brake motor 2 rotates forward, the brake clamps brake disc A, and brakes the wheel.

[0067] S3.3. The parking lock mechanism 5 is powered off, the electromagnetic force disappears, and the locking friction plate 522 is pushed backward by the spring force and presses against the following friction plate 521, thereby preventing the rotor shaft 21 of the brake motor 2 from rotating and realizing the parking brake function.

[0068] The parking brake release process includes the following steps:

[0069] S4.1. Detect vehicle motion information, and the onboard electronic control unit sends a parking brake release signal to the brake.

[0070] S4.2. The parking lock mechanism 5 is powered on, generating electromagnetic force that overcomes the spring force, pushing the locking friction plate 522 forward and separating it from the follower friction plate 521. This releases the restriction on the rotation of the rotor shaft 21 of the brake motor 2, and the parking brake is released.

[0071] like Figure 9As shown, the control method of the electronic mechanical brake with a symmetrical double-screw structure is as follows: when the front brake caliper body 12 and the rear brake caliper body 13 move toward each other and there is a brake gap between them and the brake disc A, the control mode of the brake motor 2 adopts a speed mode, aiming to make the brake motor 2 rotate at the highest speed to quickly eliminate the brake gap; when the front brake caliper body 12 and the rear brake caliper body 13 contact the brake disc A and the brake gap between them and the brake disc A is eliminated, the control mode of the brake motor 2 adopts a torque mode to quickly follow the target clamping force.

[0072] The method for judging the elimination of brake clearance is: calibrate the brake motor 2 to obtain the brake clearance elimination time T 0. If the braking time T Less than the time to eliminate the brake clearance T 0, the front brake caliper body 12 and the rear brake caliper body 13 do not contact the brake disc A; when the braking time T Equal to the time it takes to eliminate the brake clearance T 0, the brake clearance is eliminated.

[0073] For the brake motor 2 body, since the brake motor 2 runs in the speed mode before the brake gap is eliminated, the brake motor 2 mainly overcomes the inertia of the entire brake during this process. After the brake gap is eliminated, the resistance encountered by the brake motor 2 will change suddenly. At this time, if the brake motor 2 is still running in the speed mode, the angular velocity of the brake motor 2 will increase with further clamping. ω and angular acceleration β Based on this, the method for calibrating the brake motor 2 to obtain the brake clearance elimination time is as follows: the brake pedal opening is stepped on to 100%, so that the front brake caliper 12 and the rear brake caliper 13 clamp the brake disc A, and in the process, the precise contact probability of the front brake caliper 12 and the rear brake caliper 13 contacting the brake disc A is calculated in real time based on fuzzy control. P 精确 , and get the exact contact probability P 精确 and corrected braking time t of P 精确 - t curve; P 精确 - t The maximum value of the curve corresponds to the contact moment, and the corresponding correction braking time is t Time for eliminating brake clearance T 0. Considering that the brakes are frequently used during driving, the brake clearance elimination time needs to be recalibrated regularly;

[0074] Among them, the precise contact probability is calculated based on fuzzy control P 精确 The method is:

[0075] The first input variable of the fuzzy control is the angular velocity of the brake motor 2 , the second input variable is the angular acceleration of the brake motor 2 , and the output variable is the contact probability of the front brake caliper body 12 and the rear brake caliper body 13 contacting the brake disc A.

[0076] First, fuzzification is performed to divide the input variables and output variables into fuzzy sets and determine the corresponding Gaussian membership function:

[0077] The first input variable is the angular velocity of the brake motor 2 ω The domain of discourse is [0, ω max ], ω max is the maximum angular velocity of the brake motor 2; the domain is evenly divided into n ω angular velocity fuzzy sets ; Gaussian membership function of angular velocity fuzzy set for , where i ω is the number of the angular velocity fuzzy set, i ω =1~ n ω , for The central value of , for The standard deviation of , takes a fixed value;

[0078] Second input variable: angular acceleration of brake motor 2 β The domain of discourse is [- β 2, β 1], where - β 2 is the maximum angular deceleration when the brake motor 2 decelerates, β 1 is the maximum angular acceleration of the brake motor 2 when accelerating; the domain is divided into n 1 forward acceleration fuzzy set , a zero acceleration fuzzy set ZE and n 2 negative deceleration fuzzy sets ; Gaussian membership function of forward accelerating fuzzy sets for , where is the number of the forward acceleration fuzzy set, =1~ n 1, for The central value of , for Standard deviation, fixed value; Gaussian membership function of zero acceleration fuzzy set for , where C ZE for The central value of C ZE =0, for The standard deviation of , takes a fixed value; Gaussian membership function of negative deceleration fuzzy set for , where is the number of the negative deceleration fuzzy set, =1~ n 2, for The central value of , for The standard deviation of , takes a fixed value;

[0079] Output variable contact probability P The domain of discourse is [0,1], which is divided evenly into n P contact probability fuzzy set ; Gaussian membership function of contact probability fuzzy set for , where is the number of the contact probability fuzzy set, for The central value of , for The standard deviation of , takes a fixed value.

[0080] Then, fuzzy reasoning is performed to establish the angular velocity and angular acceleration variation characteristics of the brake motor 2 according to the brake clearance. H Fuzzy rules To cover various situations at different stages of the braking process:

[0081] The acceleration phase before the front brake caliper 12 and the rear brake caliper 13 come into contact with the brake disc A: the angular velocity of the brake motor 2 ω for , angular acceleration of brake motor 2 β for , contact probability P for ;

[0082] Uniform speed stage: angular velocity of brake motor 2 ω for , angular acceleration of brake motor 2 β for ZE , contact probabilityP for CP 1;

[0083] The deceleration phase after the front brake caliper 12 and the rear brake caliper 13 come into contact with the brake disc A: the angular velocity of the brake motor 2 ω for , angular acceleration of brake motor 2 β for , contact probability P for ;

[0084] Abnormal working condition: Braking motor 2 angular velocity ω for , angular acceleration of brake motor 2 β for , contact probability P for CP 1.

[0085] Then calculate the activation strength of the fuzzy rules and perform rule aggregation:

[0086] No. i The activation strength of the fuzzy rules α i for:

[0087] ;

[0088] Where, i is the number of the fuzzy rule, i =1~ H , and They are i The angular velocity of the brake motor 2 corresponding to the fuzzy rules ω and angular acceleration of brake motor 2 β Gaussian membership function.

[0089] For the activated fuzzy rules, the corresponding contact probability fuzzy sets are aggregated according to their activation strength, and the outputs of all fuzzy rules are superimposed. for:

[0090] ;

[0091] Where, For the i Activation intensity under fuzzy rules α i The weighted output variable Gaussian membership function, .

[0092] Finally, the centroid method is used for defuzzification: the contact probability P Divide into hCalculate the weighted sum to get P 精确 :

[0093] ;

[0094] Where, L is the contact probability P equal parts h The number of copies, L =0~ h , P L For the L Probability of contact in equal parts P .

[0095] like Figure 10 As shown, in a specific embodiment, fuzzification is first performed, and the first input variable is the angular velocity of the braking motor 2 ω The domain of discourse is [0,837.76], which is divided into 10 angular velocity fuzzy sets S 1~ S 10 The specific parameters of its Gaussian membership function are shown in Table 1.

[0096] Table 1

[0097]

[0098] Second input variable: angular acceleration of brake motor 2 β The domain of the word is [-200,500], which is divided into 5 positive acceleration fuzzy sets PB 1~ PB 5. 1 zero acceleration fuzzy set ZE and three negative deceleration fuzzy sets NB 1~ NB 3. The specific parameters of its Gaussian membership function are shown in Table 2.

[0099] Table 2

[0100]

[0101] Output variable contact probability P The domain of is [0,1], which is divided into 10 fuzzy sets CP 1~ CP 10 The specific parameters of its Gaussian membership function are shown in Table 3.

[0102] Table 3

[0103]

[0104] Then, fuzzy reasoning is performed. According to the change characteristics of the angular velocity and angular acceleration of the brake motor 2 when the brake clearance is eliminated, multiple fuzzy rules are established to cover various situations at different stages of the braking process, as shown in Table 4.

[0105] Table 4

[0106]

[0107] The above lists 17 fuzzy rules, but they are actually the summary and classification of 90 fuzzy rules generated by superimposing 10 fuzzy rules of the first input variable and 9 fuzzy rules of the second input variable. The reasons are as follows:

[0108] Pre-contact acceleration phase ( ω for S 1~ S 9, β for PB 1~ PB 5): During the acceleration phase when the brake gap is eliminated, the brake motor (2) drives the front brake caliper (12) and the rear brake caliper (13) to approach the brake disc (A), but they have not yet made contact. ω The increase (from S 1 to S 9), the probability of contact has increased (from CP 1 to CP 6), but the overall level is still low, because at this time there is a gap between the front brake caliper body (12) and the rear brake caliper body (13) and the brake disc (A), and there is no actual contact.

[0109] Uniform speed stage ( ω for S 1~ S 9, β for ZE ): When the brake motor (2) is in a uniform speed state ( β = ZE ),regardless ω At any level, it means that the gap has been eliminated but the front brake caliper body (12) and the rear brake caliper body (13) have not yet contacted the brake disc (A), so the contact probability is CP 1, which means there is no contact.

[0110] Post-contact deceleration phase ( ω for S 10 , β for NB 1~ NB 3): When the brake motor (2) reaches the peak speed ( ω = S 10) and the angular acceleration becomes negative, it indicates that the front brake caliper (12) and the rear brake caliper (13) have contacted the brake disc (A). As the absolute value of the negative acceleration increases (from NB 1 to NB 3) As the degree of contact deepens, the probability of contact also increases accordingly (from CP 7 to CP 10 ).

[0111] Abnormal working conditions ( ω for S 1~ S 9, β for NB 1~ NB 3): At low speed ( S 1~ S 9) negative acceleration occurs ( NB 1~ NB 3) This does not conform to the normal braking process logic. It may be motor reversal, failure or other abnormal conditions. Therefore, it is considered that there is no contact. The contact probability is CP 1.

[0112] Then the activation strength of the fuzzy rules is calculated and rule aggregation is performed.

[0113] Finally, the centroid method is used to perform defuzzification processing to obtain the accurate contact probability P 精确 .

[0114] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0115] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "back", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0116] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A control method for an electromechanical brake with a symmetrical double-screw structure, characterized by: The brake is used to brake a brake disc (A), and comprises a brake mechanism (1); The brake mechanism (1) comprises two lead screws (11), a front brake caliper body (12) and a rear brake caliper body (13); The lead screws (11) are arranged in the front-to-back direction and are divided into two sections; the thread rotation directions of the front lead screw (11) and the rear lead screw (11) are opposite, and the front nut (111) and the rear nut (112) are respectively threadedly connected; the two lead screws (11) can rotate synchronously; The front brake caliper body (12) and the rear brake caliper body (13) are respectively arranged on the front and rear sides of the brake disc (A); the left and right sides of the front brake caliper body (12) are respectively fixed to the two front nuts (111); the left and right sides of the rear brake caliper body (13) are respectively fixed to the two rear nuts (112); The two lead screws (11) rotate synchronously, and the front brake caliper body (12) and the rear brake caliper body (13) move toward each other along with the front nut (111) and the rear nut (112), respectively. When they move to clamp the brake disc (A), braking is achieved; the two lead screws (11) rotate synchronously in the opposite direction, and the front brake caliper body (12) and the rear brake caliper body (13) move in the opposite direction along with the front nut (111) and the rear nut (112), respectively, to release the brake disc (A) and release the brake; The control method is as follows: when the front brake caliper body (12) and the rear brake caliper body (13) move toward each other and a brake gap exists between them and the brake disc (A), the control mode of the brake motor (2) adopts a speed mode; when the front brake caliper body (12) and the rear brake caliper body (13) contact the brake disc (A) and the brake gap between them and the brake disc (A) is eliminated, the control mode of the brake motor (2) adopts a torque mode; The method for determining whether the brake clearance is eliminated is as follows: calibrating the brake motor (2) to obtain the brake clearance elimination time; if the braking time is less than the brake clearance elimination time, the front brake caliper body (12) and the rear brake caliper body (13) are not in contact with the brake disc (A); when the braking time is greater than or equal to the brake clearance elimination time, the brake clearance is eliminated; The method for calibrating the brake motor (2) to obtain the brake clearance elimination time is as follows: the brake pedal opening is stepped on to 100%, so that the front brake caliper (12) and the rear brake caliper (13) clamp the brake disc (A), and in the process, the precise contact probability of the front brake caliper (12) and the rear brake caliper (13) contacting the brake disc (A) is calculated in real time based on fuzzy control. P 精确 , and get the exact contact probability P 精确 and corrected braking time t of P 精确 - t curve; P 精确 - t Corrected braking time corresponding to the maximum value of the curve t Time for eliminating brake clearance; Among them, the precise contact probability is calculated based on fuzzy control P 精确 The method is: The first input variable of the fuzzy control is the angular velocity of the brake motor (2), the second input variable is the angular acceleration of the brake motor (2), and the output variable is the contact probability of the front brake caliper body (12) and the rear brake caliper body (13) contacting the brake disc (A); First, fuzzification is performed to divide the input variables and output variables into fuzzy sets and determine the corresponding Gaussian membership functions; Then, fuzzy reasoning is performed to establish multiple fuzzy rules to cover various situations at different stages of the braking process according to the characteristics of the angular velocity and angular acceleration of the braking motor (2) when the braking gap is eliminated; Then the activation strength of fuzzy rules is calculated and rule aggregation is performed; Finally, the centroid method is used to perform defuzzification processing to obtain the accurate contact probability P 精确 .

2. The control method of the electromechanical brake with a symmetrical double-screw structure according to claim 1, characterized in that: The method for performing fuzzification is: First input variable: angular velocity of brake motor (2) ω The domain of discourse is [0, ω max ], ω max is the maximum angular velocity of the brake motor (2); the domain is evenly divided into n ω angular velocity fuzzy sets ; Gaussian membership function of angular velocity fuzzy set for , where i ω is the number of the angular velocity fuzzy set, i ω =1~ n ω , for The central value of , for The standard deviation of , takes a fixed value; Second input variable: angular acceleration of the brake motor (2) β The domain of discourse is [- β 2, β 1], where - β 2 is the maximum angular deceleration of the brake motor (2) during deceleration, β 1 is the maximum angular acceleration of the brake motor (2) during acceleration; the domain is divided into n 1 forward acceleration fuzzy set , a zero acceleration fuzzy set ZE and n 2 negative deceleration fuzzy sets ; Gaussian membership function of forward accelerating fuzzy sets for , where is the number of the forward acceleration fuzzy set, =1~ n 1, for The central value of , for Standard deviation, take a fixed value; Gaussian membership function of zero acceleration fuzzy set for , where C ZE for The central value of C ZE =0, for The standard deviation of , takes a fixed value; Gaussian membership function of negative deceleration fuzzy set for , where is the number of the negative deceleration fuzzy set, =1~ n 2, for The central value of , for The standard deviation of , takes a fixed value; Output variable contact probability P The domain of discourse is [0,1], which is divided evenly into n P contact probability fuzzy set ; Gaussian membership function of contact probability fuzzy set for , where is the number of the contact probability fuzzy set, for The central value of , for The standard deviation of , takes a fixed value.

3. The control method of the electromechanical brake with a symmetrical double-screw structure according to claim 2, characterized in that: In the fuzzy reasoning, we establish H Fuzzy rules ,include: Acceleration phase: Braking motor (2) angular velocity ω for , angular acceleration of the brake motor (2) β for , contact probability P for ; Uniform speed stage: Braking motor (2) angular velocity ω for , angular acceleration of the brake motor (2) β for ZE , contact probability P for CP 1; Deceleration phase: Braking motor (2) angular velocity ω for , angular acceleration of the brake motor (2) β for , contact probability P for ; Abnormal working condition: Braking motor (2) angular velocity ω for , angular acceleration of the brake motor (2) β for , contact probability P for CP 1.

4. The control method of the electromechanical brake with a symmetrical double-screw structure according to claim 3, characterized in that: The method for calculating the activation strength of fuzzy rules and performing rule aggregation is: No. i The activation strength of the fuzzy rules α i for: ； Where, i is the number of the fuzzy rule, i =1~ H , and They are i The angular velocity of the brake motor (2) corresponding to the fuzzy rules ω and the angular acceleration of the brake motor (2) β Gaussian membership function of ; For the activated fuzzy rules, the corresponding contact probability fuzzy sets are aggregated according to their activation strength, and the outputs of all fuzzy rules are superimposed. for: ； Where, For the i Activation intensity under fuzzy rules α i The weighted output variable Gaussian membership function, ; The method for performing defuzzification processing is: P Divide into h Calculate the weighted sum to get P 精确 : ； Where, L is the contact probability P equal parts h The number of copies, L =0~ h , P L For the L Probability of contact in equal parts P .

5. An electromechanical brake having a symmetrical double-screw structure using the control method according to any one of claims 1 to 4, characterized in that: comprising a braking mechanism (1); The brake mechanism (1) comprises two lead screws (11), a front brake caliper body (12) and a rear brake caliper body (13); The lead screws (11) are arranged in the front-to-back direction and are divided into two sections; the thread rotation directions of the front lead screw (11) and the rear lead screw (11) are opposite, and the front nut (111) and the rear nut (112) are respectively threadedly connected; the two lead screws (11) can rotate synchronously; The front brake caliper body (12) and the rear brake caliper body (13) are respectively arranged on the front and rear sides of the brake disc (A); the left and right sides of the front brake caliper body (12) are respectively fixed to the two front nuts (111); the left and right sides of the rear brake caliper body (13) are respectively fixed to the two rear nuts (112); The two lead screws (11) rotate synchronously, and the front brake caliper body (12) and the rear brake caliper body (13) move toward each other along with the front nut (111) and the rear nut (112), respectively. When they move to clamp the brake disc (A), braking is achieved; the two lead screws (11) rotate synchronously in the opposite direction, and the front brake caliper body (12) and the rear brake caliper body (13) move in the opposite direction along with the front nut (111) and the rear nut (112), respectively, loosening the brake disc (A) and releasing the brake.

6. The electromechanical brake with a symmetrical double-screw structure according to claim 5, characterized in that: It also includes a brake motor (2) and a gear reduction mechanism (3); The brake motor (2) is decelerated by the gear reduction mechanism (3) and drives the two lead screws (11) to rotate synchronously; The two lead screws (11) have the same thread rotation direction and the same rotation direction.

7. The electromechanical brake with a symmetrical double-screw structure according to claim 6, characterized in that: The brake motor (2) is arranged between two lead screws (11), and the gear reduction mechanism (3) is arranged at the front end of the brake motor (2); The gear reduction mechanism (3) includes a mounting plate (31) and a first-stage reduction assembly (32) and a second-stage reduction assembly (33) arranged on the front and rear sides of the mounting plate (31); the first-stage reduction assembly (32) includes a first-stage driving gear (321) and two first-stage driven gears (322); the second-stage reduction assembly (33) includes two second-stage driving gears (331) and two second-stage driven gears (332); The two first-stage driven gears (322) are both externally meshed with the first-stage driving gear (321); the brake motor (2) drives the first-stage driving gear (321) to rotate, and the two first-stage driven gears (322) rotate synchronously therewith; The two primary driven gears (322) and the two secondary driving gears (331) are in one-to-one correspondence and are coaxially mounted on both sides of the mounting plate (31); The two secondary driving gears (331) rotate synchronously with their corresponding primary driven gears (322); The two secondary driven gears (332) are respectively externally meshed with the two secondary driving gears (331) and rotate synchronously therewith; The front ends of the two lead screws (11) are respectively fixed to the two secondary driven gears (332) and rotate synchronously therewith; The electronic mechanical brake further comprises a housing (4); the lead screw (11) is mounted in the housing (4) via a pair of deep groove ball bearings (113).

8. The electromechanical brake with a symmetrical double-screw structure according to claim 6, characterized in that: Also included is a parking lock mechanism (5); The parking lock mechanism (5) is capable of locking the rotor shaft (21) of the brake motor (2).

9. The electromechanical brake with a symmetrical double-screw structure according to claim 8, characterized in that: The parking lock mechanism (5) comprises a spring electromagnet unit (51) and a friction plate unit; The spring electromagnet unit (51) is composed of an electromagnet and a spring; when power is on, the electromagnetic force overcomes the spring force, and the spring electromagnet unit (51) shortens; when power is off, the electromagnetic force disappears, and the spring electromagnet unit (51) extends under the action of the spring force; The friction plate unit includes a follower friction plate (521) and a locking friction plate (522); the follower friction plate (521) is fixed to the rotor shaft (21) of the brake motor (2) and rotates with the rotor shaft (21); the locking friction plate (522) is fixed to the spring electromagnet unit (51) and moves with the shortening and lengthening of the spring electromagnet unit (51); When the spring electromagnet unit (51) is de-energized and extends, the locking friction plate (522) moves toward the following friction plate (521) to press the following friction plate (521), and the rotor shaft (21) is locked; when the spring electromagnet unit (51) is energized and shortened, the locking friction plate (522) moves away from the following friction plate (521), and the rotor shaft (21) is unlocked.

10. The electromechanical brake with a symmetrical double-screw structure according to claim 9, characterized in that: The brake motor (2) is arranged between two lead screws (11), and the parking lock mechanism (5) is arranged on the rear side of the brake motor (2); The front brake caliper body (12) is box-shaped, and the parking lock mechanism (5) is located inside the front brake caliper body (12); The rear brake caliper body (13) matches the front brake caliper body (12) and is hoe-shaped.

11. The electromechanical brake with a symmetrical double-screw structure according to claim 5, characterized in that: Brake friction pads (14) are fixed on the sides of the front brake caliper body (12) and the rear brake caliper body (13) facing the brake disc (A); A plurality of balls are provided between the lead screw (11), the front nut (111) and the rear nut (112).

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