A control method for a wheel-side electric drive device integrating power steering and independent drive

Abstract

The present invention discloses a control method for a power steering and independent drive integrated wheel side electric drive device, step 1, collecting vehicle speed, accelerator pedal opening and steering wheel torque, and obtaining a target total driving torque T d And the target steering wheel steering assist torque T a ; Step 2: Calculate the target force F loaded on the rack required for rack movement a , distribute the differential power steering rack force F a1 And the dual-rotor motor power steering rack force F a2 ; Step 3, calculate the left and right wheel drive torque difference, step 4, calculate the left and right wheel drive torque; step 5, calculate the dual rotor motor outer rotor output torque T w .

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a control method for a power steering and independent drive integrated wheel side electric drive device.

[0002] The present invention is a divisional application based on application number 201710247964X, invention name: A power steering and independent drive integrated wheel-side electric drive device and its control method. Background Art

[0003] Distributed drive electric vehicles mainly include hub drive and wheel side drive. Hub drive increases the unsprung mass, and the tire ground dynamic load is large, which affects the ride smoothness and maneuverability. At the same time, in order to arrange the hub motor, the steering system and suspension need to be redesigned. Compared with hub drive, wheel side drive can also have the advantages of independent drive of each wheel in the form of hub motor drive without increasing the unsprung mass, and the steering system and suspension can use existing technology, and the overall performance is better.

[0004] The electric power steering system can control the power-assisting motor to achieve power assistance according to the optimized power-assisting characteristics, and can simultaneously achieve light steering at low speeds and good road feel at high speeds, improving handling stability and driver comfort. It is the most widely used steering system form. There are three main forms of existing electric power steering systems, namely steering shaft power-assisting type, gear power-assisting type and rack power-assisting type.

[0005] The steering shaft-assisted electric power steering system minimizes the space occupied by the steering gear, but because the motor is close to the driver, the fluctuation and noise of the motor output torque can be easily transmitted to the steering wheel, thus affecting driving comfort and road feel; the gear-assisted electric power steering system integrates the torque sensor, motor, reduction mechanism and clutch together, and the motor directly drives the gear shaft through the reduction mechanism to assist, which has a complex structure and a high failure rate. The rack-assisted electric power steering system achieves assistance by directly applying the power torque to the rack. The system has good rigidity, large force transmission capacity, and compact structure. At the same time, it is not restricted by the installation position, and the fluctuation of the motor is not easily transmitted to the steering wheel, which improves driving comfort. However, the rack-assisted electric power steering system requires a large output torque because the power assist position is below the steering gear. In order to improve economy, it is generally powered by 24V or 48V DC voltage, which requires an additional DC conversion circuit. This adds extra cost to the existing 12V DC-powered traditional cars. Even for electric vehicles, no matter what form of electric power steering system, an additional steering power motor and its reduction mechanism are required to complete the required power assist function. Summary of the invention

[0006] Based on the above background, the present invention also designs and develops a control method for a wheel-side electric drive device integrating power steering and independent drive. The purpose of the present invention is to utilize the differential power steering function that can be achieved by independent drive to apply additional power to the steering of the vehicle and obtain additional output torque.

[0007] The technical solution provided by the present invention is:

[0008] A power steering and independent drive integrated wheel side electric drive device, comprising:

[0009] A dual-rotor motor, wherein the inner rotor is connected to the first driving half shaft to drive the wheels on one side, and the outer rotor is connected to the driving gear through the output shaft to drive the driving gear to rotate;

[0010] A driving motor, a rotor of which is connected to the second driving half shaft and is used to drive the wheel on the other side;

[0011] A rack screw shaft, both ends of which are respectively hinged to steering tie rods;

[0012] The driven gear, whose center hole cooperates with the thread pair of the rack screw shaft, can drive the rack screw shaft to move and realize steering under the drive of the driving gear;

[0013] The driving gear is meshed with the intermediate gear shaft gear, and the driven gear is meshed with the intermediate gear shaft gear.

[0014] Preferably, the invention further comprises a steering control system, comprising:

[0015] A steering wheel, the center of which is connected to the steering shaft;

[0016] A steering wheel torque sensor, which is mounted on the steering shaft and is used to detect the torque of the steering wheel;

[0017] Wherein, the rack screw shaft includes a rack portion located on one side and a screw portion located in the middle, the rack portion is meshed with the steering gear at the lower end of the steering shaft, and the screw portion cooperates with the center hole screw pair of the driven gear.

[0018] Preferably, the dual-rotor motor comprises:

[0019] A housing having a housing therein for arranging an outer rotor and an inner rotor;

[0020] Permanent magnets are embedded on the inner and outer surfaces of the outer rotor;

[0021] a stator fixed on the inner surface of the housing;

[0022] an excitation winding fixed on the stator and passing current to generate a magnetic field;

[0023] an armature winding mounted on the inner rotor;

[0024] The outer rotor output shaft of the dual-rotor motor is connected to the driving gear for outputting torque, and the inner rotor output shaft is connected to the first driving half shaft for outputting driving torque for driving the vehicle.

[0025] Preferably, the driving motor comprises:

[0026] A housing having a housing space therein for arranging a rotor;

[0027] Permanent magnets, which are embedded on the rotor surface;

[0028] a stator fixed on the inner surface of the housing;

[0029] an excitation winding fixed on the stator and passing current to generate a magnetic field;

[0030] an armature winding mounted on the inner rotor;

[0031] Wherein, the rotor output shaft of the driving motor is connected to the second driving half shaft for driving the wheel on the other side.

[0032] Preferably, the outer rotor of the dual-rotor motor includes a main body and an end cover that fit together in a toothed manner, and the inner rotor of the dual-rotor motor is nested in the accommodating space formed by the main body and the end cover through upper and lower bearing supports, and its output end passes through the accommodating space to connect to the inner rotor output shaft.

[0033] Preferably, it also includes:

[0034] The driven gear has a semicircular spiral groove processed on the inner wall of the center hole, and an inner circulation channel is also processed on the inner wall along the axial direction, and the inlet and outlet of the channel are respectively at the starting point and the end point of the semicircular spiral groove;

[0035] Wherein, a semicircular spiral groove is arranged on the rack screw shaft, and the position of the semicircular spiral groove corresponds to the position of the driven gear;

[0036] The balls roll along the semicircular spiral groove and the inner circulation channel.

[0037] Preferably,

[0038] A first driving half shaft, one end of which is connected to the inner rotor output shaft of the dual-rotor motor through a universal joint for inputting driving force;

[0039] A second driving half shaft, one end of which is connected to the rotor output shaft of the driving motor through a universal joint for inputting driving force;

[0040] A steering knuckle, which is supported on the wheel hub and the wheel through a wheel hub bearing and has a hollow journal;

[0041] Wherein, the tie rod is connected to the steering knuckle via a ball stud.

[0042] Preferably, it also includes:

[0043] A central processing unit connected to the dual-rotor motor via a CAN bus;

[0044] Wherein, the steering wheel torque sensor is electrically connected to the central processing unit, and the central processing unit controls the torque of the dual-rotor motor through the steering wheel torque.

[0045] A control method for a wheel-side electric drive device integrated with power steering and independent drive, comprising the following steps:

[0046] Step 1: Collect vehicle speed, accelerator pedal opening and steering wheel torque to obtain the target total driving torque T d And the target steering wheel steering assist torque T a ;

[0047] Step 2: Calculate the target force F on the rack required for rack movement a , distribute the differential power steering rack force F a1 And the dual-rotor motor power steering rack force F a2 , the calculation formula is as follows:

[0048] F a =T a / r p ,

[0049] F a1 =kF a ,

[0050] F a2 =(1-k)F a ,

[0051] In the formula, F a The force applied to the rack to move the target, F a1 To distribute the differential power steering rack force, F a2 The dual-rotor motor power steering rack force, T a is the target steering wheel steering assist torque, r p is the radius of the steering gear pinion, k is the differential power steering distribution coefficient, k = 0 ~ 1;

[0052] Step 3: Calculate the left and right wheel drive torque difference ΔT, the calculation formula is as follows:

[0053]

[0054] Where ΔT is the difference in driving torque between the left and right wheels, N is the transmission ratio from rack translation displacement to steering knuckle angular displacement, and r w is the rolling radius of the wheel, r σ It is the lateral offset distance of the main pin contact;

[0055] Step 4: Calculate the left and right wheel drive torques. The calculation formula is as follows:

[0056] T d =T r +T l ,

[0057] ΔT=|T r -T l |,

[0058] Where, T d is the target total driving torque, T r is the output torque of the inner rotor of the dual-rotor motor, T l is the output torque of the drive motor, where when the car turns left, T r >T l , when the car turns right, T r <T l ;

[0059] Step 5: Calculate the output torque T of the outer rotor of the dual-rotor motor w , the calculation formula is as follows:

[0060]

[0061] Where, T w is the output torque of the outer rotor of the dual-rotor motor, i1 is the transmission ratio of the driving gear to the intermediate gear shaft gear, i2 is the transmission ratio of the gear pair from the intermediate gear shaft gear to the driven gear, d2 is the middle diameter of the ball screw mechanism, and λ is the lead angle of the ball screw mechanism.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] 1. Good system integration: The power steering and independent drive integrated wheel-side electric drive device of the present invention realizes the electric power steering function in addition to the independent drive function of the traditional wheel-side drive system by using a dual-rotor motor and a ball screw mechanism. That is, the integration of the steering system and the drive system is realized;

[0064] 2. Compact structure: The power steering and independent drive integrated wheel-side electric drive device of the present invention uses a dual-rotor motor to provide driving torque and steering power torque at the same time, and adopts a ball screw mechanism to achieve deceleration and torque increase and motion conversion. Compared with the traditional electric power steering system, it has a small size and a more compact structure, and is not restricted by the installation position.

[0065] 3. Differential drive can be used to coordinate steering assistance, thereby achieving energy-saving steering. The integrated power steering and independent drive wheel-side electric drive device described in the present invention can give full play to the technical advantages of independent wheel-side motor drive of the left and right wheels, and use the difference in driving torque of the left and right wheels to generate a ground driving force difference, thereby generating a differential power steering torque to coordinate with the dual-rotor motor arranged on one side to complete the power steering, so that the power steering torque demand of the dual-rotor motor can be reduced, achieving energy-saving steering.

[0066] 4. Good driving comfort: When the power steering and independent drive integrated wheel-side electric drive device described in the present invention provides power steering, the torque fluctuation and noise generated by the motor are not easily transmitted to the driver, which greatly improves driving comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a three-dimensional view of a power steering and independent drive integrated wheel-side electric drive device described in the present invention.

[0068] Figure 2 The present invention provides a simplified structural diagram of a power steering and independent drive integrated wheel-side electric drive device.

[0069] Figure 3 This is a full cross-sectional view of a ball screw mechanism of a power steering and independently driven integrated wheel-side electric drive device described in the present invention.

[0070] Figure 4 The isometric view of the ball screw mechanism nut of the power steering and independent drive integrated wheel side electric drive device described in the present invention.

[0071] Figure 5 This is an axonometric view of the outer rotor of a dual-rotor motor of a power steering and independently driven integrated wheel-side electric drive device described in the present invention.

[0072] Figure 6 This is an axonometric view of the inner rotor of a dual-rotor motor of a power steering and independently driven integrated wheel-side electric drive device described in the present invention.

[0073] Figure 7 This is an electrical connection diagram of a power steering and independently driven integrated wheel-side electric drive device described in the present invention.

[0074] Figure 8The present invention is a flow chart of a control method for a power steering and independent drive integrated wheel-side electric drive device. DETAILED DESCRIPTION

[0075] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0076] It should be understood that terms such as “having”, “including” and “comprising” used herein do not specify the existence or addition of one or more other elements or combinations thereof. Figure 1-7 It shows an implementation example of the content of the present invention, but is not limited to this form. Any system that uses a dual-rotor motor to achieve integrated power steering and independent drive belongs to the scope of protection. In addition, the directional words used in the specification of the present invention, such as "up", "down", "left", "right", "front", "back", etc., are only directional words used in conjunction with this example and its drawings for the convenience of discussion, and do not mean that the structure shown in the example can only be arranged and installed in this orientation. In actual use, the orientation and connection relationship can be changed according to the actual layout space. Simply changing the orientation and layout relationship does not constitute a new structure different from the present invention.

[0077] like Figure 1 As shown, the power steering and independent drive integrated wheel-side electric drive device described in the present invention includes: a steering control system 100, a left wheel drive system 300, a steering power execution system 400, a left drive motor 500, a dual-rotor motor 600, and a right wheel drive system 700.

[0078] like Figure 1 , 2 In the embodiment shown, the dual-rotor motor 600 includes a housing 670, an outer rotor 610, an inner rotor 620, a permanent magnet 630, an excitation winding 640, a stator 650, and an armature winding 660. The housing 670 is used to accommodate the outer rotor 610 and the inner rotor 620; the permanent magnet 630 is attached to the inner and outer surfaces of the outer rotor 610; the stator 650 is fixed to the housing 670; the excitation winding 640 is installed on the stator 650; and the armature winding 660 is installed on the inner rotor 620. Figure 5In the illustrated embodiment, the outer rotor 610 of the dual-rotor motor 600 includes a main body 611 and an end cover 612 that are mutually matched in a tooth-embedded manner. The center of the front end surface of the main body 611 has a stepped through hole composed of a bearing hole with a slightly larger inner diameter and a light hole with a smaller inner diameter. The bearing hole is used to install the upper support bearing of the inner rotor 620. A bearing countersunk hole is processed on the inner side of the bottom of the end cover 612 for installing the lower support bearing of the inner rotor 620. At the same time, an external spline is processed on the output shaft end of the end cover 612 for spline connection with the driving gear 440. The inner rotor 620 is nested in the accommodation space formed by the main body 611 and the end cover 612 that are mutually matched in a tooth-embedded manner.

[0079] During installation, first install the upper end of the inner rotor 620 and the bearing inside the outer rotor 610 body 611, then put on the outer rotor end cover 612, and then install the outer rotor 610 and the inner rotor 620 as a whole into the dual-rotor steering motor housing 670. The dual-rotor motor housing is fixed on the frame and arranged on the suspension, which belongs to the sprung mass.

[0080] In another embodiment, if Figure 5 As shown, six arc trapezoidal groove teeth are processed on the circumference of the matching place between the rear end of the main body 611 and the end cover 612, that is, the size of the groove tooth at the radial near-center end is smaller than that at the far-center end, and the tooth root plane of the groove tooth is also processed with a circular arc-shaped small groove; six arc trapezoidal protruding teeth are processed at the corresponding positions of the end cover 612 and the six arc trapezoidal grooves of the main body 611, and the size of the protruding tooth at the radial near-center end is smaller than that at the far-center end, and the tooth top plane of the arc trapezoidal protruding tooth is also processed with a circular arc-shaped protrusion corresponding to the small groove at the tooth root of the arc trapezoidal groove teeth of the main body, and the arc trapezoidal protrusion and the arc trapezoidal groove are basically the same size. When the main body 611 and the end cover 612 are combined into the outer rotor 610, the arc trapezoidal groove teeth of the main body 611 and the corresponding arc trapezoidal protruding teeth of the end cover are positioned on both sides of the tooth shape, which plays a role in radial positioning, so that the centers of the two are aligned, and the small grooves of the respective tooth heels and the arc-shaped protrusions of the tooth-setting circular rings are matched with each other in clearance, which plays a role in auxiliary radial limiting and axial positioning, ensuring reliable centering when the main body 611 and the end cover 612 are engaged.

[0081] The dual-rotor motor is a double-end output structure, wherein the output end of the inner rotor 620 of the dual-rotor motor is connected to the right inner universal joint 740 via a spline, and the output end of the outer rotor 610 is connected to the driving gear 440 via a spline.

[0082] In another embodiment, if Figure 2As shown, the left drive motor 500 is a common single-rotor motor, which is composed of a stator 550, a rotor 520, a permanent magnet 530, an excitation winding 540 and a motor housing 510. Among them, the stator 550 is fixed on the motor housing 510, and the excitation winding 540 is installed on the stator 550, and the permanent magnet 530 is fixed on the rotor 520. The output end of the left drive motor 500 is the output shaft end of the rotor 520, and the top of the output end is processed with an external spline for connecting with the left inner universal joint 340. The left drive motor housing is fixed on the frame and arranged on the suspension, which belongs to the sprung mass.

[0083] like Figure 1 , Figure 2 As shown, the left wheel drive system 300 comprises a left outer half shaft 310, a left outer universal joint 320, a left inner half shaft 330, a left inner universal joint 340, a left steering knuckle 350, and a left wheel 360. The left inner universal joint 340 and the left outer universal joint 320 are both constant angular velocity universal joints. The journal portion of the left steering knuckle 350 is hollow so that the outer half shaft 310 can pass through it.

[0084] like Figure 1 , Figure 2 As shown, the right drive system 700 includes a right outer half shaft 710, a right outer universal joint 720, a right inner half shaft 730, a right inner universal joint 740, a right steering knuckle 750, and a right wheel 760. The right inner universal joint 340 and the right outer universal joint 320 are both constant angular velocity universal joints. The journal portion of the right steering knuckle 750 is made hollow so that the outer half shaft 710 can pass through it.

[0085] The left drive system 300 and the right drive system 700 are completely identical in composition, structure and component structures.

[0086] like Figure 1 , Figure 2 As shown, the output end of the inner rotor 620 of the dual-rotor motor 600 and the inner end of the right inner half shaft 730 are connected through the right inner universal joint 740, and the outer end of the right inner half shaft 730 and the inner end of the right outer half shaft 710 are connected through the right outer universal joint 720. The outer end of the right outer half shaft 710 is processed with a flange, and six evenly distributed bolts are processed on the flange. The flange of the right outer half shaft 710 is fixedly connected to the hub of the right wheel 760 through bolts and nuts, so that the right outer half shaft 710 can drive the right wheel 760 to rotate.

[0087] like Figure 1 , Figure 2As shown, the output end of the left driving motor 500 is connected to the inner end of the left inner half shaft 330 via the left inner universal joint 340, and the outer end of the left inner half shaft 330 is connected to the inner end of the left outer half shaft 310 via the left outer universal joint 320. The outer end of the left outer half shaft 310 is processed with a flange, and six bolts are processed on the flange. The flange of the left outer half shaft 310 is fixedly connected to the wheel hub of the left wheel 360 by bolts and nuts, so that the left outer half shaft 310 can drive the left wheel 360 to rotate.

[0088] In another embodiment, if Figure 1 , 2 As shown in , 3 and 4, the power steering actuator system 400 is composed of a ball screw mechanism nut 410, an intermediate gear shaft gear 420, a rack screw shaft 430, a driving gear 440, an intermediate gear shaft 450 and a ball 460. The ball 460, the rack screw shaft 430 and the ball screw mechanism nut 410 form a ball screw nut pair, and the function of the ball screw nut pair is to convert the rotational motion of the outer rotor 610 of the dual-rotor motor into the linear motion of the rack screw shaft 430 through the special function of the ball screw nut mechanism. The rack screw shaft 430 and the rack in the steering gear 160 are integrated structures, and a semicircular spiral groove is processed on the rack screw shaft 430 as a track for the rolling of the ball 460; the ball screw mechanism nut 410 is a gear shaft shape, and the inner wall of the nut center is processed with a semicircular spiral groove corresponding to the screw 430, which is used to assemble the ball 460 and serve as a track for the sliding of the ball 460, and the hole wall is a light hole. At the same time, there is an inner circulation channel for the ball processed in the axial direction of the inner wall of the nut 410, and the entrance and exit of the channel are respectively near the starting point and the end point of the semicircular spiral groove. The ball circulation channel enables the ball 460 to circulate and roll in the track, realizing the conversion of the rotational motion of the nut 410 into the linear motion of the screw 430. The driven gear 401 in the middle of the nut 410 of the ball screw mechanism is a common spur gear, which meshes with the common cylindrical spur gear 420 on the intermediate gear shaft 450. The intermediate gear shaft 450 is supported on the steering gear housing through a pair of angular contact ball bearings. The driving gear 440 is a common cylindrical spur gear, and a spline hole corresponding to the spline at the output end of the dual-rotor motor outer rotor 610 is processed in the center thereof, so as to be connected to the output shaft end of the dual-rotor motor outer rotor 610. The driving gear 440 meshes with the intermediate gear shaft gear 420, and its pressure angle and module are the same as those of the intermediate gear shaft gear 420.

[0089] In another embodiment, if Figure 1 , 2As shown, the steering control system 100 is composed of a steering wheel 101, a steering shaft 110, a steering wheel torque sensor 120, a first universal joint 130, a steering transmission shaft 140, a second universal joint 150, a steering gear 160, a steering gear left housing 170, a steering gear right housing 180, and a steering tie rod 190. The center of the steering wheel 101 is connected to the steering shaft 110, and the steering shaft is equipped with a steering wheel torque sensor 120. The lower end of the steering shaft 110 is connected to the input end of the steering transmission shaft 140 through the first universal joint 130, and the output end of the steering transmission shaft 140 is connected to the input end of the second universal joint 150, and the output end of the second universal joint 150 is connected to the input end of the steering gear 160.

[0090] The gear rack steering gear selected for the steering gear 160 includes a steering input pinion, a gear rack, and a steering gear housing. The gear rack and the screw of the ball screw mechanism are processed as one body to form a gear rack screw shaft 430. The centers of both ends of the gear rack screw shaft 430 are processed with threaded holes for installing ball studs, which are connected to the left and right steering tie rods 190 through the ball studs, and the left and right steering tie rods 190 are respectively connected to the left steering knuckle 350 and the right steering knuckle 750 through the ball studs. It is worth noting that although the present invention uses a gear rack steering gear, it is not limited to the use of a gear rack steering gear, and other forms of steering gears are all acceptable, and this does not constitute a limitation on the scope of protection of the claims described in the present invention.

[0091] like Figure 1 , Figure 2 , Figure 3 As shown, the steering gear housing is divided into a left steering gear housing 170 and a right steering gear housing 180, which are connected and fixed by bolts and nuts, wherein a driving gear 440, an intermediate gear shaft 450, and a ball screw mechanism nut 410 are installed in parallel, wherein a thrust bearing 190 is installed between the left and right outer walls of the ball screw mechanism nut 410 and the left and right steering gear housings to limit the horizontal movement of the ball screw mechanism nut 410. Both the driving gear 440 and the intermediate gear shaft 450 are supported on the steering gear housing by bearings. The steering gear housing is fixed to the frame and arranged on the suspension, and belongs to the sprung mass.

[0092] like Figure 1 , Figure 2As shown, the specific connection relationship of the components is as follows: the output end of the inner rotor 620 of the dual-rotor motor is connected to the inner end of the right inner half shaft 730 through the right inner universal joint 740, the other end of the right inner half shaft 730 is connected to the inner end of the right outer half shaft 710 through the outer universal joint 720, the right outer half shaft 710 passes through the center of the hollow journal of the right wheel steering knuckle 750, and the right outer half shaft 710 and the hub of the right wheel 760 are connected by a flange on the right outer half shaft 710 with a uniformly distributed The output shaft end of the left drive motor 500 is connected to the inner end of the left inner half-shaft 330 through the left inner universal joint 340, and the other end of the left inner half-shaft 330 is connected to the inner end of the left outer half-shaft 310 through the left outer universal joint 320. The left outer half-shaft 310 passes through the center of the hollow journal of the left wheel steering knuckle 350, and the left outer half-shaft 310 and the wheel hub of the left wheel 360 are fixed with evenly distributed bolts and nuts through the flange on the left outer half-shaft 310. The center of the steering wheel 101 is connected to the steering shaft 110, and a steering wheel torque sensor 120 is installed on the steering shaft 110. The lower end of the steering shaft 110 is connected to the input end of the steering drive shaft 140 through the first universal joint 130, and the output end of the steering drive shaft 140 is connected to the input end of the second universal joint 150, and the output end of the second universal joint 150 is connected to the input end of the steering gear 160. The rack of the steering gear 160 and the screw of the ball screw mechanism are processed as one body to form a rack screw shaft 430. The two ends of the rack screw shaft 430 are respectively connected to the left and right steering tie rods 190 through ball pins, and the left and right steering tie rods 190 are respectively connected to the left wheel steering knuckle 350 and the right wheel steering knuckle 750 through ball pins. The output shaft of the outer rotor 610 of the dual-rotor motor fixes the driving gear 440 through a spline, and the driving gear 440 meshes with the intermediate gear shaft gear 420. The driving gear 440 and the intermediate gear shaft 450 are supported on the steering gear housing through a pair of angular contact ball bearings. The lead screw of the ball screw mechanism and the rack of the steering gear 160 are processed into one piece to form a rack screw shaft 430. The driven gear 401 on the nut 410 of the ball screw mechanism meshes with the intermediate gear shaft gear 420. A thrust bearing 190 is installed at each axial end of the nut 410 of the ball screw mechanism. The thrust bearings 190 are installed on the left steering gear housing 170 and the right steering gear housing 180 respectively, so that the linear motion of the ball screw mechanism nut 410 along the lead screw is limited, so that it can only rotate around the axis of the rack screw shaft 430, thereby driving the rack screw shaft 430 to move linearly.

[0093] In another embodiment, if Figure 7 As shown, the steering wheel torque sensor 120 is connected to the central processing unit (ECU) through a cable, and the ECU is connected to the dual-rotor motor 600 through a cable. The ECU can read the steering wheel torque signal measured by the steering wheel torque sensor 120, and is connected to the vehicle CAN bus at the same time, and can read the vehicle speed and other signals of the CAN bus. The ECU can control the dual-rotor motor 600.

[0094] The specific working process and working principle of the steering and driving integrated wheel-side electric drive system described in the present invention are as follows:

[0095] The inner rotor 620 of the dual-rotor motor is controlled to generate a driving torque, which is transmitted to the hub of the right wheel 760 via the right inner universal joint 740, the inner half shaft 730, the outer universal joint 720 and the outer half shaft 710, thereby driving the right wheel 760 to rotate; similarly, the controlled rotor of the left drive motor 500 outputs a driving torque, which is transmitted to the hub of the left wheel 360 via the left inner universal joint 340, the left inner half shaft 330, the left outer universal joint 320 and the left outer half shaft 310, thereby driving the left wheel 360 to rotate.

[0096] When driving straight, the driving torques output by the inner rotor 620 of the dual-rotor motor 600 and the left drive motor 500 are equal; when the car turns, since the torques of the wheel-side motors on both sides can be controlled separately, the drive motors of the left and right wheels on the inside and outside of the curve (i.e., the dual-rotor motor and the left drive motor) can output unequal torques, so that a left-right driving force difference will be generated on the ground. This driving force difference and the lateral offset distance of the tire ground contact kingpin can be used to generate a differential power steering torque, which together with the power steering torque output by the outer rotor of the dual-rotor motor assists the driver in completing the steering action, reduces the driver's steering burden, and improves the ease of steering.

[0097] When the driver operates the steering wheel 101 to rotate, the steering wheel 101 drives the steering shaft 110 to rotate, and the steering wheel torque sensor 120 measures the torque applied by the driver and transmits the signal to the central control unit (ECU). The ECU reads the corresponding power-assist torque from the power-assist characteristic curve diagram stored in the ECU in combination with the vehicle speed signal, and calculates the winding current corresponding to the power-assist torque generated by the outer rotor 610 of the dual-rotor motor. The ECU sends a control instruction to the outer rotor 610 of the dual-rotor motor, and the outer rotor 610 of the dual-rotor motor generates a power-assist torque. The power-assist torque is directly applied to the rack 430 via the driving gear 440, the intermediate gear shaft gear 420 and the ball screw mechanism. The power-assist torque is superimposed on the steering torque applied by the driver on the rack 430, thereby pulling the steering tie rod 190 to make the left wheel 360 and the right wheel 760 rotate through a corresponding angle, thereby realizing the function of electric power steering.

[0098] like Figure 8 As shown, the control method of the power steering and independent drive integrated wheel side electric drive device described in the present invention is specifically as follows:

[0099] Step 1: System program initialization, the controller reads vehicle speed, accelerator pedal opening, steering wheel torque and other vehicle driving status signals;

[0100] Step 2: First, the target total driving torque T is obtained by looking up the table according to the vehicle speed and accelerator pedal opening signal. d Secondly, the target steering wheel steering assist torque T is obtained by looking up the table based on the vehicle speed and steering wheel torque signal. a The required data table is pre-calibrated and stored in the ECU;

[0101] Step 3: Calculate the target force F on the rack required to move the rack a , the calculation formula is as follows:

[0102] F a =T a / r p ,

[0103] Among them, F a The force applied to the rack to move the target, T a is the target steering wheel steering assist torque, r p is the radius of the steering gear pinion; the power assist F a Together with the movement force applied by the driver to the rack, it pushes the wheels to deflect around the kingpin to complete the steering.

[0104] Step 4: Distribute the differential power steering rack force F a1 and dual rotor motor power steering rack force F a2 , the calculation formula is as follows:

[0105] F a1 =kF a ,

[0106] F a2 =(1-k)F a

[0107] Among them, F a1 To distribute the differential power steering rack force, F a2 is the dual-rotor motor power steering rack force, k (value between 0 and 1) is defined as the differential power steering distribution coefficient, when k = 1, all are differential power steering; when k = 0, all are dual-rotor motor power steering. In general driving conditions, k = 0, and in energy-saving driving conditions, k> 0. The specific value of k is determined according to the principle that the torque of each motor after distribution is less than the most economical working torque of the motor at the current speed, so as to ensure that the total energy demand is saved as much as possible.

[0108] Step 5: Calculate the left and right wheel drive torque difference ΔT, the calculation formula is as follows:

[0109]

[0110] Where ΔT is the difference in driving torque between the left and right wheels, N is the transmission ratio of rack translation displacement to steering knuckle angular displacement (unit: m / rad); r w is the rolling diameter of the wheel; r σ It is the lateral offset distance of the kingpin ground contact.

[0111] Step 6: Calculate the left and right wheel drive torque commands according to the following two formulas:

[0112] T d =T r +T l ,

[0113] ΔT=|T r -T l |,

[0114] Among them, T d is the target total driving torque, T r is the output torque of the inner rotor of the dual-rotor motor, T l The output torque of the left drive motor. When the differential power steering requires the car to turn left, T r >T l ; When the car turns right, T r <T l .

[0115] Finally, the inner rotor torque control command of the dual-rotor motor is output to the dual-rotor motor and the left drive motor torque control command is output to the left drive motor.

[0116] Step 7: Calculate the output torque T of the outer rotor of the dual-rotor motor w Instruction, T w The calculation formula is as follows:

[0117]

[0118] Where, T w is the output torque of the outer rotor of the dual-rotor motor, i1 is the transmission ratio of the driving gear 440 to the intermediate gear shaft gear 420, i2 is the transmission ratio of the gear pair from the intermediate gear shaft gear 420 to the driven gear 401 on the nut 410 of the ball screw mechanism, d2 is the middle diameter of the ball screw mechanism, and λ is the lead angle of the ball screw mechanism.

[0119] Finally, the outer rotor torque control command of the dual-rotor motor is output to the dual-rotor motor.

[0120] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A control method for a wheel-side electric drive device integrated with power steering and independent drive, characterized in that: The device includes: A dual-rotor motor, wherein the inner rotor is connected to the first driving half shaft to drive the wheels on one side, and the outer rotor is connected to the driving gear through the output shaft to drive the driving gear to rotate; A driving motor, a rotor of which is connected to the second driving half shaft and is used to drive the wheel on the other side; The rack screw shaft has two ends respectively connected to the steering tie rods; the rack and the screw of the ball screw mechanism are processed as one to form the rack screw shaft; The driven gear, whose center hole cooperates with the thread pair of the rack screw shaft, can drive the rack screw shaft to move and realize steering under the drive of the driving gear; The driving gear is meshed with the intermediate gear shaft gear, and the driven gear is meshed with the intermediate gear shaft gear; The control method comprises the following steps: Step 1: Collect vehicle speed, accelerator pedal opening and steering wheel torque to obtain the target total driving torque T d And the target steering wheel steering assist torque T a ; Step 2: Calculate the target force F on the rack required for rack movement a , distribute the differential power steering rack force F a1 And the dual-rotor motor power steering rack force F a2 , the calculation formula is as follows: F a =T a / r p , F a1 =kF a , F a2 =(1-k)F a , In the formula, F a The force applied to the rack to move the target, F a1 To distribute the differential power steering rack force, F a2 The dual-rotor motor assist steering rack force, T a is the target steering wheel steering assist torque, r p is the radius of the steering gear pinion, k is the differential power steering distribution coefficient, k = 0 ~ 1; Step 3: Calculate the left and right wheel drive torque difference ΔT, the calculation formula is as follows: Where ΔT is the difference in driving torque between the left and right wheels, N is the transmission ratio from rack translation displacement to steering knuckle angular displacement, and r w is the rolling radius of the wheel, r σ It is the lateral offset distance of the main pin contact; Step 4: Calculate the left and right wheel drive torques. The calculation formula is as follows: T d =T r +T l , ΔT=|T r -T l |, Where, T d is the target total driving torque, T r is the output torque of the inner rotor of the dual-rotor motor, T l is the output torque of the drive motor, where when the car turns left, T r >T l , when the car turns right, T r <T l ; Step 5: Calculate the output torque T of the outer rotor of the dual-rotor motor w , the calculation formula is as follows: Where, T w is the output torque of the outer rotor of the dual-rotor motor, i1 is the transmission ratio of the driving gear to the intermediate gear shaft gear, i2 is the transmission ratio of the gear pair from the intermediate gear shaft gear to the driven gear, d2 is the middle diameter of the ball screw mechanism, and λ is the lead angle of the ball screw mechanism.

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