JP2008092682A - Electric cart - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric cart of novel constitution capable of sufficiently enhancing cornering performance. <P>SOLUTION: A yaw moment calculating part 43 applies to the formula (3) the tire transverse forces Fya, Fyb of respective rear wheels 5a, 5b computed by a tire transverse force computing unit 39 and the tire longitudinal forces Fxa, Fxb of respective rear wheels 5a, 5b computed by a tire longitudinal force computing unit 41 to compute yaw moment YM. A motor torque command value computing unit 45 computes the first motor torque command value TP1 of a first electric motor 7 and the second motor torque command value TP2 of the second electric motor 11 so as to eliminate the difference between the computed yaw moment YM and a target yaw moment GYM. A motor control unit 47 controls the first electric motor 7 and the second electric motor 11 based on the computed first motor torque command value TP1 and the second motor torque command value TP2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric cart such as an electric racing cart using an electric motor.

  In recent years, with the spread of motor sports, carts such as racing carts have been used by a wide range of age groups. Also, a cart such as a racing cart is usually driven to rotate with the left and right rear wheels as drive wheels, and the left and right rear wheels are integrally rotated by a common engine or electric motor. .

In addition, there exist some which are shown to patent document 1 and patent document 2 as a prior art relevant to this invention.
JP-A-2005-231391 JP 2004-180800 A

  By the way, as described above, since the cart such as a racing cart drives the left and right rear wheels, if the engine torque of the engine or the motor torque of the electric motor increases, the tendency of oversteering during cornering is strong. This may cause spin. On the other hand, if the engine torque of the engine or the motor torque of the electric motor is reduced during cornering to try to avoid spin, the cart turning speed cannot be sufficiently secured. In short, the conventional cart has a problem that it is extremely difficult to improve cornering performance.

  Therefore, an object of the present invention is to provide an electric cart having a novel configuration that can sufficiently improve cornering performance.

  The first feature of the present invention (the feature of the invention described in claim 1) is detected in an electric cart that is driven to rotate independently by a first electric motor and a second electric motor with left and right rear wheels as drive wheels. Vehicle center-of-gravity position correcting means for correcting the center-of-gravity position of the vehicle based on the wheel load of each rear wheel and the detected wheel load of each front wheel, and the rear wheel based on the detected steering angle and the detected vehicle body speed. Slip angle calculating means for calculating the slip angle of the vehicle, slip ratio calculating means for calculating the slip ratio of each rear wheel based on the detected vehicle speed and the detected wheel speed of each rear wheel, and tire lateral force The tire lateral force data indicating the relationship between the slip angle and the wheel load is applied with the calculated slip angle of the rear wheel and the detected wheel load of each rear wheel to obtain the tire lateral force of each rear wheel. Calculate tire lateral force Applying the calculated slip ratio of each rear wheel and the detected wheel load of each rear wheel to the tire longitudinal force data indicating the relationship between the means, the tire longitudinal force, the slip ratio, and the wheel load, Based on the calculated tire lateral force of each rear wheel and the calculated tire longitudinal force of each rear wheel, the corrected vehicle center-of-gravity position is calculated. Yaw moment calculating means for calculating a surrounding yaw moment, and a first motor torque command value of the first electric motor and a second motor of the second electric motor so as to eliminate the difference between the calculated yaw moment and the target yaw moment. Motor torque command value calculation means for calculating a torque command value, and the first electric motor and the second electric motor based on the calculated first motor torque command value and second motor torque command value. And motor control means for controlling the motor, and summarized in that provided with the.

  According to the first feature, the yaw moment calculating means includes the tire lateral force of each rear wheel calculated by the tire lateral force calculating means and the tire front and rear of each rear wheel calculated by the tire longitudinal force calculating means. The yaw moment around the center of gravity of the vehicle is calculated based on the force, and the motor torque command value calculation means calculates the first motor torque of the first electric motor so as to eliminate the difference between the calculated yaw moment and the target yaw moment. A command value and a second motor torque command value of the second electric motor are calculated, and the motor control means calculates the first electric motor and the second motor torque command value based on the calculated first motor torque command value and second motor torque command value. In order to control the second electric motor, the motor torque of the entire electric motor (the motor torque of the first electric motor and the motor of the second electric motor) Without reducing the torque sum), it can be varied according to the motor torque and the motor torque of the second electric motor of the first electric motor to a change in cornering situation of the electric cart. Specifically, the motor torque of the second electric motor is sufficiently larger than the motor torque of the first electric motor during left cornering, and the motor torque of the first electric motor is increased to the second electric motor during right cornering. It can be made sufficiently larger than the motor torque of the motor.

  Here, the vehicle gravity center position correcting means corrects the vehicle gravity center position based on the detected wheel load of each rear wheel and the detected wheel load of each front wheel, and the yaw moment calculating means is corrected. Since the yaw moment around the center of gravity of the vehicle is calculated, the actual yaw moment can be accurately obtained even if the driver's posture changes greatly during cornering, and the motor torque of the first electric motor and the The motor torque of the second electric motor can be accurately varied according to the change in the cornering state of the electric cart.

  In addition to the first feature, the second feature of the present invention (feature of the invention described in claim 2) is a target yaw moment correcting means for correcting the target yaw moment based on the corrected vehicle center-of-gravity position, The motor torque command value calculating means includes a first motor torque command value for the first electric motor and a second electric motor so as to eliminate a difference between the calculated yaw moment and the corrected target yaw moment. The gist is that the second motor torque command value is calculated.

  According to a third feature of the present invention (a feature of the invention described in claim 3), in addition to the first feature or the second feature, the target yaw moment is set to be neutral steer. The gist.

  According to a fourth feature of the present invention (a feature of the invention described in claim 4), in addition to any one of the first to third features, the tire lateral force data includes the tire lateral force and It is a tire lateral force map showing the relationship between the slip angle and the wheel load, and the tire longitudinal force data is summarized as being a tire longitudinal force map showing the relationship between the tire longitudinal force, the slip ratio, and the wheel load.

  A fifth feature of the present invention (a feature of the invention described in claim 5) is that, in addition to any one of the first to third features, the tire lateral force data includes the tire lateral force and It is a relational expression of a magic formula indicating the relationship between the slip angle and the wheel load, and the tire longitudinal force data is summarized as being a relational expression of the magic formula indicating the relation between the tire longitudinal force, the slip ratio, and the wheel load.

  According to the invention according to any one of claims 1 to 5, the first motor torque of the first electric motor and the first motor torque can be reduced without reducing the motor torque of the entire electric motor. Since the second motor torque of the two electric motors can be accurately varied in accordance with the change in the cornering state of the electric cart, stable cornering can be performed while sufficiently securing the turning speed of the electric cart. The cornering performance of the cart can be sufficiently increased.

  In particular, according to the invention of any one of claims 3 to 5, since the target yaw moment is set to be neutral steer, the steering characteristic of the electric cart is set to neutral steer. Alternatively, it can be kept close to neutral steer, and the cornering performance of the electric cart can be greatly improved.

  An embodiment of the present invention will be described with reference to FIGS.

  Here, FIG. 1 is a control block diagram of the electric racing cart according to the embodiment of the present invention, FIG. 2 is a schematic plan view of the electric racing cart according to the embodiment of the present invention, and FIG. 3 is a CPU in the controller. 4 is a flowchart of a series of motor control processes according to FIG. 4, FIG. 4 is a diagram illustrating tire lateral force / tire longitudinal force of each rear wheel, and yaw moment around the vehicle center of gravity, and FIG. 5 (a) is a tire lateral force map. FIG. 5B is a diagram showing the tire longitudinal force.

  As shown in FIG. 2, an electric racing cart 1 according to an embodiment of the present invention is one of electric carts, and includes a vehicle body frame 3 as a base. Further, left and right rear wheels 5a and 5b are rotatably provided at the rear portion of the vehicle body frame 3, and left and right front wheels 5c and 5d are rotatably provided at the front portion of the vehicle body frame 3. A first electric motor 7 is provided at the left rear portion of the vehicle body frame 3, and the output shaft of the first electric motor 7 is connected to the rotation shaft of the left rear wheel 5a with a gear mechanism 9 or a chain mechanism (not shown). (Not shown). Similarly, a second electric motor 11 is provided at the right rear portion of the vehicle body frame 3, and the output shaft of the second electric motor 11 is connected to the rotating shaft of the right rear wheel 5b with a gear mechanism 13 or a chain mechanism ( (Not shown). That is, the electric racing cart 1 is driven to rotate independently by the first electric motor 7 and the second electric motor 11 using the left and right rear wheels 5a and 5b as driving wheels.

  A steering wheel 15 that snakes the left and right front wheels 5c and 5d is provided at the front portion of the vehicle body frame 3. Although not shown, a seat on which a driver is seated is disposed at the center of the body frame 3, and an accelerator pedal and a brake pedal are provided at the front of the body frame 3, respectively.

  In the vicinity of the rear wheels 5a and 5b, wheel load detection sensors 17a and 17b for detecting the wheel loads Fza and Fzb of the rear wheels 5a and 5b are provided, respectively, and in the vicinity of the front wheels 5c and 5d. Wheel load detection sensors 17c and 17d for detecting wheel loads Fzc and Fzd of the front wheels 5c and 5d are provided. Further, a steering angle detection sensor 19 for detecting a steering angle δ is provided in the vicinity of the wheel shaft of the steering wheel 15 in the vicinity of each rear wheel 5c, 5d. A vehicle speed detection sensor 21 for detecting the vehicle speed V is provided. Further, wheel speed detection sensors 23a and 23b for detecting wheel speeds Sa and Sb are provided in the vicinity of the rear wheels 5a and 5b, respectively.

  As shown in FIGS. 1 and 2, the body frame 3 is provided with a controller 25 for controlling the first electric motor 7 and the second electric motor 11, and the controller 25 includes a wheel load detection sensor. 17a, 17b, 17c, 17d, steering angle detection sensor 19, vehicle body speed detection sensor 21, and wheel speed detection sensors 23a, 23b are electrically connected. The controller 25 interprets a ROM (not shown) that stores a motor control program for controlling the first electric motor 7 and the second electric motor 11, and a motor control program stored in the ROM. CPU (not shown) to be executed and a RAM (not shown) for providing a work area for the CPU. The ROM in the controller 25 has a function as the tire lateral force data storage unit 27 and a function as the tire longitudinal force data storage unit 29, and the CPU in the controller 25 serves as the vehicle gravity center position correction unit 31. Functions, functions as a target yaw moment correction unit 33, functions as a slip angle calculation unit 35, functions as a slip ratio calculation unit 37, functions as a tire lateral force calculation unit 39, functions as a tire longitudinal force calculation unit 41, It has a function as a yaw moment calculation unit 43, a function as a motor torque command value calculation unit 45, and a function as a motor control unit 47. The details of each function are as follows.

  That is, the tire lateral force data storage unit 27 stores a tire lateral force map (see FIG. 5A) showing the relationship among the tire lateral force Fy, the slip angle θ, and the wheel load Fz as tire lateral force data. . A large number of actual tire lateral force maps are prepared for each wheel load Fz. The tire lateral force data storage unit 27 stores, as tire lateral force data, a relational expression of a magic formula indicating the relationship between the tire lateral force Fy, the slip angle θ, and the wheel load Fz instead of the tire lateral force map. It doesn't matter.

  The tire longitudinal force data storage unit 29 stores a tire longitudinal force map (see FIG. 5B) showing the relationship among the tire longitudinal force Fx, the slip ratio α, and the wheel load Fz as tire longitudinal force data. A large number of actual tire longitudinal force maps are prepared for each wheel load Fz. The tire longitudinal force data storage unit 29 may store a relational expression of a magic formula indicating a relationship among the tire longitudinal force Fx, the slip ratio α, and the wheel load Fz instead of the tire longitudinal force map.

  The vehicle center-of-gravity position correcting unit 31 includes the wheel loads Fza and Fzb of the rear wheels 5a and 5b detected by the wheel load detection sensors 17a and 17b and the wheels of the front wheels 5c and 5d detected by the wheel load detection sensors 17c and 17d. Based on the loads Fzc and Fzd, the vehicle center-of-gravity position GC is corrected.

  The target yaw moment correcting unit 33 corrects the target yaw moment GYM set to be neutral steer based on the vehicle equation of motion based on the vehicle center of gravity position GC corrected by the vehicle center of gravity position correcting unit 31. is there.

The slip angle calculation unit 35 calculates the vehicle body speed V detected by the vehicle body speed detection sensor 21 and the steering angle δ detected by the steering angle detection sensor 19.
θ = f (δ, V)... is applied to equation (1) to calculate the slip angle θ.

The slip ratio calculation unit 37 calculates the vehicle body speed V detected by the vehicle body speed detection sensor 21 and the wheel speeds Sa and Sb of the rear wheels 5a and 5b detected by the wheel speed detection sensors 23a and 23b.
α = (V−S) / S Applying to the equation (2), the slip ratios αa and αb are calculated.

  The tire lateral force calculating unit 39 calculates the slip angle θ of the rear wheels 5a and 5b calculated by the slip angle calculating unit 35 and the wheel loads Fza and Fzb of the rear wheels 5a and 5b detected by the wheel load detection sensors 17a and 17b. Is applied to the tire lateral force map stored in the tire lateral force data storage unit 27 to calculate the tire lateral forces Fya and Fyb (see FIG. 4) of the rear wheels 5a and 5b.

  The tire longitudinal force calculating unit 41 calculates the slip rates αa and αb of the rear wheels 5a and 5b calculated by the slip rate calculating unit 37 and the wheel loads of the rear wheels 5a and 5b calculated by the wheel load detection sensors 17a and 17b. Fza and Fzb are applied to the tire longitudinal force map stored in the tire longitudinal force data storage unit 29 to calculate the tire longitudinal forces Fxa and Fxb (see FIG. 4) of the rear wheels 5a and 5b.

The yaw moment calculation unit 43 includes the tire lateral forces Fya and Fyb of the rear wheels 5a and 5b calculated by the tire lateral force calculation unit 39 and the tire front and rear of the rear wheels 5a and 5b calculated by the tire longitudinal force calculation unit 41. Forces Fxa and Fxb
YM = −Lr (Fya + Fyb) −1/2 Wt (Fxa−Fxb) (3)
To calculate the yaw moment YM (see FIG. 4) around the corrected vehicle center of gravity position GC. In the equation (4), Wt is a tread of the electric racing cart 1, and Lr is a distance in the front-rear direction between the axles of the rear wheels 5a and 5b and the corrected vehicle center of gravity GC (see FIG. 4). ).

  The motor torque command value calculation unit 45 is configured to eliminate the difference between the yaw moment YM calculated by the yaw moment calculation unit 43 and the target yaw moment GYM corrected by the target yaw moment correction unit 33. The motor torque command value TP1 and the second motor torque command value TP2 of the second electric motor 11 are calculated.

  The motor control unit 47 controls the first electric motor 7 and the second electric motor 11 based on the first motor torque command value TP1 and the second motor torque command value TP2 calculated by the motor torque command value calculation unit 45. It is. More specifically, the motor control unit 47 controls the current value supplied to the first electric motor 7 and the current value supplied to the second electric motor 11.

  Next, a series of motor control processes by the CPU in the controller 25 will be described with reference to FIG. Note that a series of motor control processes by the CPU in the controller 25 is executed every predetermined cycle (for example, 4 msec).

  First, the CPU in the controller 25 executes input signal detection processing for various detection sensors (step 1). Specifically, the CPU in the controller 25 detects input signals from the wheel load detection sensors 17a, 17b, 17c, 17d, the steering angle detection sensor 19, the vehicle body speed detection sensor 21, and the wheel speed detection sensors 23a, 23b. .

  After the end of step 1, the CPU in the controller 25 executes a vehicle gravity center position / target yaw moment correction process (step 2). Specifically, the CPU (vehicle center-of-gravity position correcting unit 31) in the controller 25 determines the detected wheel loads Fza and Fzb of the rear wheels 5a and 5b and the detected wheel loads Fzc and Fzd of the front wheels 5c and 5d. Based on this, the vehicle center of gravity position GC is corrected. Then, the CPU (target yaw moment correction unit 33) in the controller 25 corrects the target yaw moment GYM based on the corrected vehicle center-of-gravity position GC.

  After the end of step 2, the CPU in the controller 25 executes a calculation process of the slip ratio, slip angle, and wheel load (step 3). Specifically, the CPU (slip angle calculation unit 35) in the controller 25 calculates the slip angle θ by applying the detected steering angle δ and the detected vehicle speed V to the equation (1). In addition, the CPU (slip rate calculation unit 37) in the controller 25 applies the detected vehicle speed V and the detected wheel speeds Sa and Sb of the rear wheels 5a and 5b to the above equation (2) to thereby determine the slip rate. αa and αb are calculated.

  After the end of step 3, the CPU in the controller 25 executes a tire lateral force / tire longitudinal force calculation process (step 4). Specifically, the CPU (tire lateral force calculation unit 39) in the controller 25 uses the calculated slip angle θ of the rear wheels 5a and 5b and the detected wheel loads Fza and Fzb of the rear wheels 5a and 5b to the side of the tire. Applying to the force map, the tire lateral forces Fya and Fyb of the rear wheels 5a and 5b are calculated. Further, the CPU (tire front / rear force calculation unit 41) in the controller 25 uses the calculated slip rates αa, αb of the rear wheels 5a, 5b and the detected wheel loads Fza, Fzb of the rear wheels 5a, 5b before and after the tires. Applying to the force map, the tire longitudinal force Fxa, Fxb of each rear wheel 5a, 5b is calculated.

  After the end of step 4, the CPU in the controller 25 executes yaw moment calculation processing (step 5). Specifically, the CPU (yaw moment calculator 43) in the controller 25 calculates the calculated tire lateral forces Fya and Fyb of the rear wheels 5a and 5b and the calculated tire longitudinal forces Fxa and of the rear wheels 5a and 5b. Fxb is applied to the equation (4) to calculate the yaw moment YM around the corrected vehicle center-of-gravity position GC.

  After the end of step 5, the CPU in the controller 25 executes a motor torque command value calculation process (step 6). Specifically, the CPU (motor torque command value calculation unit 45) in the controller 25 performs the first electric motor so as to eliminate the difference between the calculated yaw moment YM and the target yaw moment GYM set to be neutral steer. The first motor torque command value TP1 of the motor 7 and the second motor torque command value TP2 of the second electric motor 11 are calculated.

  After the end of step 6, the CPU in the controller 25 executes a motor torque control process (step 7). Specifically, the CPU (motor control unit 47) in the controller 25 controls the first electric motor 7 and the second electric motor 11 based on the calculated first motor torque command value TP1 and second motor torque command value TP2. Control.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  The yaw moment calculation unit 43 includes the tire lateral forces Fya and Fyb of the rear wheels 5a and 5b calculated by the tire lateral force calculation unit 39 and the tire front and rear of the rear wheels 5a and 5b calculated by the tire longitudinal force calculation unit 41. The yaw moment YM is calculated by applying the forces Fxa and Fxb to the equation (3), and the motor torque command value calculation unit 45 eliminates the difference between the calculated yaw moment YM and the target yaw moment GYM. The first motor torque command value TP1 of the motor 7 and the second motor torque command value TP2 of the second electric motor 11 are calculated, and the motor control unit 47 calculates the calculated first motor torque command value TP1 and second motor torque command. Since the first electric motor 7 and the second electric motor 11 are controlled based on the value TP2, the motor torque of the entire electric motor (the motor torque of the first electric motor 7 and the second electric motor The first motor torque of the first electric motor 7 and the second motor torque of the second electric motor 11 can be adjusted according to changes in the cornering state of the electric racing cart 1 without reducing the sum of the motor torques of the dynamic motor 11. Can be variable. Specifically, the motor torque of the second electric motor 11 is sufficiently larger than the motor torque of the first electric motor 7 during the left cornering, and the motor torque of the first electric motor 7 is set to the second electric motor during the right cornering. The motor torque of the motor 11 can be made sufficiently larger.

  Here, the vehicle center-of-gravity position correcting unit 33 corrects the vehicle center-of-gravity position GC based on the detected wheel loads Fza and Fzb of the rear wheels 5a and 5b and the detected wheel loads Fzc and Fzd of the front wheels 5c and 5d. The yaw moment calculator 43 calculates the yaw moment YM around the corrected vehicle center of gravity GC, so that even if the driver's posture changes greatly during cornering, the actual yaw moment YM is accurately calculated. The motor torque of the first electric motor 7 and the motor torque of the second electric motor 11 can be accurately varied according to the change in the cornering state of the electric racing cart 1.

  Therefore, according to the embodiment of the present invention, stable cornering can be easily performed while sufficiently securing the turning speed of the electric racing cart 1, and the cornering performance of the electric racing cart 1 can be sufficiently enhanced. . In particular, since the target yaw moment GYM is set to be neutral steer, the steering characteristics of the electric racing cart 1 can be maintained at a neutral steer or a state close to neutral steer, and the cornering performance of the electric racing cart 1 can be greatly improved. Can be improved.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, In addition, it can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

It is a control block diagram of the electric racing cart according to the embodiment of the present invention. 1 is a schematic plan view of an electric racing cart according to an embodiment of the present invention. It is a flowchart of a series of motor control processing by CPU in a controller. It is a figure explaining the tire lateral force of each rear wheel, the tire longitudinal force, and the yaw moment around the vehicle gravity center position. FIG. 5A shows a tire lateral force map, and FIG. 5B shows a tire longitudinal force.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric racing cart 5a, 5b Rear wheel 7 1st electric motor 11 2nd electric motor 17a, 17b, 17c, 17d Wheel load detection sensor 19 Steering angle detection sensor 21 Car body speed detection sensor 23a, 23b Wheel speed detection sensor 25 Controller 27 Tire lateral force data storage unit 29 Tire longitudinal force data storage unit 31 Vehicle center-of-gravity position correction unit 33 Target yaw moment correction unit 33 Vehicle center-of-gravity position correction unit 35 Slip angle calculation unit 37 Slip rate calculation unit 37 Wheel load calculation unit 39 Tire lateral force Calculation unit 41 Tire longitudinal force calculation unit 43 Yaw moment calculation unit 45 Motor torque command value calculation unit 47 Motor control unit

Claims (5)

In the electric cart that is driven to rotate independently by the first electric motor and the second electric motor using the left and right rear wheels as drive wheels,
Vehicle gravity center position correcting means for correcting the vehicle gravity center position based on the detected wheel load of each of the rear wheels and the detected wheel load of each front wheel;
Slip angle calculating means for calculating the slip angle of the rear wheel based on the detected steering angle and the detected vehicle speed,
Slip ratio calculating means for calculating the slip ratio of each rear wheel based on the detected vehicle speed and the detected wheel speed of each rear wheel;
Applying the calculated slip angle of the rear wheel and the detected wheel load of each rear wheel to the tire lateral force data indicating the relationship between the tire lateral force, the slip angle, and the wheel load, the tire for each rear wheel Tire lateral force calculating means for calculating lateral force;
Applying the calculated slip ratio of each rear wheel and the detected wheel load of each rear wheel to the tire longitudinal force data indicating the relationship between the tire longitudinal force, the slip ratio, and the wheel load, Tire longitudinal force calculating means for calculating tire longitudinal force;
A yaw moment calculating means for calculating a yaw moment around the corrected vehicle center of gravity based on the calculated tire lateral force of each rear wheel and the calculated tire longitudinal force of each rear wheel;
Motor torque command value calculating means for calculating the first motor torque command value of the first electric motor and the second motor torque command value of the second electric motor so as to eliminate the difference between the calculated yaw moment and the target yaw moment. ,
Motor control means for controlling the first electric motor and the second electric motor based on the calculated first motor torque command value and second motor torque command value;
An electric cart comprising: A target yaw moment correcting means for correcting the target yaw moment based on the corrected position of the center of gravity of the vehicle,
The motor torque command value calculation means is configured to eliminate the difference between the calculated yaw moment and the corrected target yaw moment, and the first motor torque command value of the first electric motor and the second motor torque of the second electric motor. The electric cart according to claim 1, wherein a command value is calculated.   The electric cart according to claim 1 or 2, wherein the target yaw moment is set to be neutral steer.   Tire lateral force data is a tire lateral force map showing the relationship between tire lateral force, slip angle and wheel load, and tire longitudinal force data is a tire longitudinal force map showing the relationship between tire longitudinal force, slip ratio and wheel load. The electric cart according to any one of claims 1 to 3, wherein:   The tire lateral force data is a relational expression of the magic formula that indicates the relationship between the tire lateral force, the slip angle, and the wheel load. The tire longitudinal force data is the magic formula that indicates the relationship between the tire longitudinal force, the slip ratio, and the wheel load. The electric cart according to any one of claims 1 to 3, wherein the electric cart is a relational expression.

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