KR101734573B1 - Steering control system for mobile using movement of upper body - Google Patents

Abstract

The present invention relates to a steering control device for a boarding vehicle using upper body movement and has a main object of providing a steering control device capable of moving the boarding device more easily and stably in a desired direction and speed from the operation of a passenger according to an upper body movement will be. In order to achieve the above-mentioned object, a fixed frame fixedly installed on a fixed frame of a boarding vehicle, a fixed frame mounted on the fixed frame via pressure sensors, A plurality of pressure sensors disposed between the fixed frame and the steering frame, and a handle mounted to move the steering frame; And a control unit for outputting a control signal for controlling a moving direction and a speed of the boarding vehicle on the basis of the detection signals of the respective pressure sensors, and a steering control apparatus for a boarding vehicle using the upper body movement is disclosed .

Description

[0001] The present invention relates to a steering control system for a vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a steering control apparatus for a passenger board, and more particularly, to a steering control apparatus for a passenger board that controls a boarding apparatus to be moved in a desired direction and speed from a passenger operation according to an upper body movement.

BACKGROUND ART [0002] Vehicles such as two-wheeled, three-wheeled, and four-wheeled vehicles that are driven by a power generating device such as a bicycle, an internal combustion engine, or an electric motor running on a man power today are widely used as moving means.

In recent years, a single-person stand-up type boarding device has been developed and used. In general, a single-person standing type boarding device has a two-wheel structure such as a segway or a winglet.

That is, the single-person stand-up type boarding device determines the moving direction and the speed by measuring the movement of the center of gravity of the occupant through the sensors while the two wheels are mounted.

At this time, the boarding device is moved in the direction in which the center of gravity is moved by calculating the movement direction and the movement amount of the center of gravity of the occupant. The controller controls driving of the driving motor mounted on the wheel according to the determined direction and speed, It is possible to turn left and right.

This allows the body to be automatically moved forward or backward, to be turned or stopped by tilting the body forward or backward, and also to prevent the occupant from falling over by using a balance mechanism like a tilt.

In such a two-wheeled boarding vehicle, when the road surface is uneven or the wheel is caught by an obstacle during driving, a sudden tilting occurs due to the characteristics of a two-wheeled vehicle.

In addition, for the beginner, there are frequent safety problems such as abrupt start of the boarding system due to the inadequate operating ability, or overturning of the board due to collision with surrounding obstacles. In order to overcome this problem, 3 wheels are applied.

However, in the case of a conventional stand-up type boarding device, it is necessary for a passenger to move the center of gravity in a direction to move using the lower body, so that the lower body is inconvenient or difficult to move the center of gravity through the lower body or a child or an elderly It is very difficult or impossible to use.

In addition, in the process of moving the center of gravity using the lower body, the user may fall off the boarding equipment due to inoperability, and the injured person may be injured.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a steering control device capable of more easily and stably moving a boarding vehicle in a desired direction and speed from an operation of a passenger according to an upper body movement .

In order to achieve the above object, the present invention provides a steering control apparatus for a boarding vehicle, comprising: a fixed frame fixedly installed on a fixed frame of the boarding device; A steering control part including a steering frame mounted to be supported by the fixed frame so as to be able to flow through the sensors, a plurality of pressure sensors disposed between the fixed frame and the steering frame, and a handle mounted to move the steering frame. Wow; And a controller for outputting a control signal for controlling a moving direction and a speed of the boarding vehicle on the basis of the detection signals of the respective pressure sensors. The steering control apparatus for a boarding vehicle using the upper body movement .

In a preferred embodiment, the control unit processes the detection signals of the respective pressure sensors to calculate a two-dimensional pressure distribution applied through the steering frame, calculates the two-dimensional pressure distribution from the calculated two-dimensional pressure distribution, And a sensor signal processing module for determining and outputting a speed; And a central processing module for outputting a control signal for controlling the moving direction and speed of the boarding device on the basis of the moving direction and the speed information applied by the sensor signal processing module.

The control unit may further include a motor control module that controls driving of a driving motor directly connected to each driving wheel of the boarding device according to a control signal applied from the central processing module.

The fixing frame of the steering operation unit is horizontally fixed to the upper portion of the fixed frame of the boarding device. The steering frame is installed on the lower side of the fixing frame with the pressure sensors interposed therebetween. The handle is fixed to left and right ends of the steering frame And the steering control device of the present invention can be configured so that the steering frame can be tilted through the handle as the occupant tilts the upper body while holding the handle with both hands.

In order to attain the above object, the steering control device of the present invention is preferably arranged such that the handle is extended back and forth at left and right ends of the steering frame so that the occupant can push or pull the steering wheel while tilting the upper body while being held by a hand.

Further, in the steering control device of the present invention for achieving the above-mentioned object, the pressure sensors may be composed of sensors whose relative positions are divided into front, rear, and right.

Accordingly, when the steering control apparatus according to the present invention is applied, the following advantages are obtained.

1) In the conventional one-person stand-up type boarding device, the center of gravity is moved through the lower body in a state where the occupant stands, so that the steering operation is difficult. In the case of applying the steering control device according to the present invention, The steering operation can be performed through the movement of the steering wheel, so that more natural steering control becomes possible, and the convenience of the occupant can be increased eventually.

2) Also, the accuracy of the steering can be increased because people are more familiar with the movement of the upper body than the lower body.

3) It is also possible for disabled persons with uncomfortable legs or hand movements to be able to operate through the movement of their upper body, and can easily adapt to use even in the case of children or elderly people who are not able to operate.

1 is a diagram showing a frame structure of a steering control apparatus and a boarding apparatus employing the steering control apparatus according to an embodiment of the present invention.
2 is a view showing an example of a boarding device employing the steering control device according to the embodiment of the present invention.
3A and 3B are perspective views showing a steering control apparatus according to an embodiment of the present invention.
4 is a block diagram showing a motor control configuration of the steering control device according to the embodiment of the present invention.
5 is a view showing the operating state of the steering control unit when the steering control apparatus according to the embodiment of the present invention is stopped, right-turned, left-turn, forward, or backward.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device of a boarding device for controlling a boarding device to move in a desired direction and speed according to the operation of a passenger, The present invention relates to a steering control device capable of easily moving forward and backward, accelerating and decelerating, and changing direction (steering operation) even in the case of a child or an elderly person.

Particularly, the steering control device of the present invention has a main characteristic in that it can move the boarding device in a desired direction and speed from the operation of the passenger according to the movement of the upper body.

FIG. 1 illustrates a frame structure of a boarding vehicle equipped with a steering control device 100 according to an embodiment of the present invention. The frame structure of a boarding vehicle in the present invention is not limited to the example shown in FIG.

2, it is possible to configure the boarding device 200 by adding a boarding structure in which the occupant 1 can lean up and down in the frame structure of Fig. 1, The present invention is not limited to the example shown in Fig. 2, but the form of the boarding device to which the steering control device of the present invention is applied is not limited to that shown in Fig.

2, the illustrated boarding device 200 includes a steering control device of the present invention (reference numeral 100 in FIG. 1) and a fixed steering control device (not shown in FIG. 1) mounted on an exterior riding structure in which the occupant 1 can be raised and tilted. (Hereinafter referred to as " 201 " in Fig. 1), and includes two front wheels 210, which are drive wheels for driving, and one rear wheel 220, which is an auxiliary wheel, Wheel structure that is rotatably mounted on the vehicle body.

The boarding device 200 may be configured to use an electric motor as a driving source for driving, and may include a driving motor (not shown) capable of transmitting rotational force to left and right front wheels 210, (211) is mounted on the fixed frame (201).

In the illustrated example, the left and right drive motors 211 are mounted directly to the respective front wheels 210 as drive wheels, and each drive motor 211 is connected to a motor control module To be driven and controlled independently.

In this configuration, when the rotational speed of the left front wheel is faster than the rotational speed of the right front wheel by the left drive motor, the boarding device makes a right turn, and if it is the opposite, the boarding device makes a left turn.

When the left and right front wheels simultaneously rotate forward, the boarding device advances. When the left and right front wheels simultaneously rotate reversely, the boarding device moves backward.

In addition, when the left and right front wheels stop at the same time, the boarding device remains in a stopped state.

Accordingly, when the driving state of each driving motor 211 is controlled by the motor control module 123 such as the torque, the rotational speed, and the rotational direction, the stopping and moving of the boarding unit 200, forward / Speed control such as constant speed and acceleration / deceleration becomes possible.

In addition, when driving the drive unit 211 by driving the boarding unit 200 as described above, a battery (reference numeral 230 in FIG. 2) serving as a power source of the boarding unit must be mounted. The battery for supplying the driving power of the driving motor in the boarding device is not shown in Fig.

In the boarding device 200 of FIG. 2, the handle 114 is positioned on both left and right sides of the boarding structure. The boarding passenger 1 falls down on the boarding structure and then holds the boarding posture In this posture, when the occupant 1 tilts the upper body in a desired direction, both hands move the knob 114 while naturally following the upper body.

Especially, according to the movement of the upper body, the hand in the rotational direction is pushed downward, and the hand in the opposite direction is naturally pulled by pulling the handle.

That is, when the occupant tilts the upper body in a direction in which the occupant wants to rotate in a prone position, the hand in the rotating direction pushes the handle and the hand in the opposite direction pulls the handle, The handle in the direction is pulled up.

For example, in order to rotate the boarding device to the right, the occupant must tilt the upper body to the right. At this time, the left hand pulls the handle upward and the right hand pushes down the handle. So that the boarding device rotates to the right.

On the other hand, when the passenger is rotated to the left, the occupant tilts the upper body to the left. At this time, the right hand pulls the handle upward, and the left hand pushes the handle down, .

In addition, if the passenger wishes to advance the passenger, the passenger tilts the upper body forward to tilt the handle forward, and the passenger advances in the direction of tilting the handle.

Conversely, if the passenger wishes to move backward, the occupant tilts the upper body backward to tilt the handle backward, and the passenger is then allowed to move backward.

The steering control using the upper body motion can be implemented by the steering control device according to the present invention, and the steering control device will be described in detail as follows.

FIGS. 3A and 3B are perspective views showing a steering control apparatus 100 according to an embodiment of the present invention, and FIG. 4 is a block diagram showing a motor control configuration of a steering control apparatus according to an embodiment of the present invention.

3A and 3B, the steering control apparatus 100 of the present invention includes a fixed frame 111 disposed on the upper side, a steering frame 112 disposed on the lower side, and a sensor for detecting a passenger operation intention A plurality of pressure sensors 113 disposed between the fixed frame 111 and the steering frame 112 and a steering handle 110 including a handle 114 installed on the steering frame 112.

In addition, the steering control device 100 according to the present invention processes a detection signal of each of the pressure sensors 113 installed in the steering control unit 110 to generate a sensor signal (signal) for determining the moving direction and the speed of the boarding vehicle, And a central processing module (122) for outputting a control signal for controlling the moving direction and speed of the boarding device based on the moving direction and the speed information inputted from the sensor signal processing module (121) And a control unit 120.

Here, the central processing module 122 controls the driving signal processing module 121 such that the driving wheel of the boarding vehicle can be rotationally driven at a moving direction and a speed determined by the sensor signal processing module 121, And to output a control signal for controlling the power generating device and the steering mechanism of the boarding device so that the steering and speed of the driving wheel can be controlled.

The front wheel 210, that is, the driving wheel is directly connected to the driving motor 211 as the power generating device, and the traveling direction and the speed of the boarding unit 200 can be controlled only by the drive control of each driving motor The control signal output from the central processing module 122 becomes a control signal for controlling the driving of each driving motor 211 according to the moving direction and the speed determined by the sensor signal processing module 121. [

The control unit 120 further includes a motor control module 123 that controls driving of each driving motor 211 according to a control signal output from the central processing module 122. The motor control module 123 An inverter (not shown) for driving the motor 211 by phase-converting the power supplied from the battery 230 through switching control such as a PWM (Pulse Width Modulation) method according to a control signal applied from the central processing module 122, ). ≪ / RTI >

1, the fixed frame 111 of the steering control unit 110 is horizontally fixed to the upper portion of the fixed frame 201 of the boarding device and includes a body portion 111a on which the pressure sensors 113 are disposed, And an upper plate 111b fixed to the upper side of the body part 111a. As illustrated, the upper plate 111b may be integrally fixed to the upper part of the fixing frame 201, or the body part 111a And may be integrally fixed to the upper portion of the fixed frame 201.

At this time, a sensor signal processing module (denoted by reference numeral 123 in FIG. 4) for receiving the detection signal of the pressure sensor 113 and determining the moving direction and speed of the passenger device and outputting a signal may be installed in the body part 111a.

In addition, a plurality of supports can be fixedly installed on the upper plate 111b downward. In FIGS. 3a and 3b, longitudinal and transverse supports 116a and 116b are shown fixed to the lower surface of the upper plate 111b , The respective supporting members may be integrally fixed to the body portion 111a, or the supporting members may be integrally fixed to the fixed frame 201 of the boarding device and supported.

At this time, the transverse support rods 116b having both ends fixed to the upper plate 111b can be installed to support the body portion 111a from the lower side, and the longitudinal support rods 116a having both ends fixed to the upper plate 111b And can be installed to support the steering frame 112 from below.

The steering frame 112 is disposed below the fixed frame 111 and is supported by the fixed frame 111 via a plurality of pressure sensors 113 or between the fixed frame 111 and the pressure sensor 113, And a handle 114 is provided at each of the left and right ends of the handle 114 to be manually operated by a passenger.

The handle 114 may be a bar-shaped handle having a U-shaped configuration and may be installed to be long in front and rear at both ends of the steering frame 112.

As described above, when the passenger grips the upper body in a desired direction in order to stop, advance and retract, accelerate / decelerate, and change the left / right direction of the boarding vehicle as described above, the handle 114 applies a force in a specific direction And the force applied through the handle is transmitted to the steering frame 112 and then detected by the pressure sensor 113. [

The pressure sensor 113 is a driver's intention detecting means for grasping the two-dimensional distribution of the force applied through the handle 114 and the steering frame 112. The pressure sensor 113 includes a plurality of At this time, all the pressure sensors 113 are individually connected to the sensor signal processing module 121 so that the detection values (pressure values) can be input.

The pressure sensors 113 are constituted by sensors whose relative positions are divided into front and rear parts and sensors whose relative positions are divided into right and left parts. Sensors classified as front and rear are arranged to move forwardly and backwardly ), And the left and right sensors are sensors for detecting a steering motion intent of a passenger who wishes to turn the boarding device to the left or right.

As shown in the figure, a total of four pressure sensors 113 can be disposed at four positions on the front and rear, left and right. However, various types of pressure distributions are available to identify the pressure sensors 113 in accordance with the back and forth, The number of the pressure sensors 113 can be variously changed so as to be precisely obtained.

In other words, if necessary, the pressure sensors are further divided into the front and rear parts, the right and left parts, and the entire pressure sensors are connected to the sensor signal processing module so that the respective detection values are separately inputted.

On the other hand, the sensor signal processing module 121 calculates and collects the two-dimensional pressure distribution applied through the steering frame 112 in the sensor installation area based on the pressure detection values collected through the pressure sensors 113.

The two-dimensional pressure distribution information is pressure distribution information of each sensor position according to the inclination of the steering frame 112, and information on the force applied by the occupant through the movement of the upper body and the movement of the hand, The two-dimensional pressure distribution information represented by the two-dimensional pressure distribution information is information indicating the passenger driving intention for stopping the vehicle, traveling forward, backward, accelerating / decelerating,

Based on the pressure measured by the pressure sensor 113, the sensor signal processing module 121 calculates the information of the force applied by the driver through the steering frame 112, that is, the two-dimensional pressure distribution, The moving direction and speed of the apparatus are determined.

The sensor signal processing module 121 outputs the moving direction and the speed information to the central processing module 122. The central processing module 122 receives the moving direction and the speed information from the sensor signal processing module 121, The motor control module 123 outputs a control signal for controlling the driving of each driving motor on the basis of the motor speed information input by the speed detecting section 212 for detecting the rotational speed of each driving motor 211. The motor control module 123 performs central processing And controls driving of each driving motor 211 according to a control signal applied from the module 122.

5A to 5E are diagrams showing operation states of the steering control unit 110 when stopping, advancing, reversing, right turning or left turning, respectively. As shown in FIG. 2, the occupant 1 climbs onto the boarding device 200 When the force is transmitted to the steering frame 112 by using the upper body and the hand in a state of being tangled, the transmitted force is detected by the pressure sensor 113 provided between the fixed frame 111 and the fixed frame 111, Driving of the driving motor 211 is controlled.

This allows the rider to move the rider in the desired direction and at the desired speed.

First, when the steering frame 112 is substantially in parallel with the fixed frame 111, it is recognized that the occupant is stopped (see Fig. 5A).

At this time, the pressure detection value of the total pressure sensor 113 is maintained within a certain range. The sensor signal processing module 121 recognizes the passenger's intention to stop from the pressure distribution state.

For example, when the difference between the maximum detection value and the minimum detection value of the front and rear pressure sensors 113 is within the set value (the steering frame and the fixed frame are approximately parallel), the sensor signal processing module 121 It is recognized that the device is to be kept stationary (recognizing the stop operation of the boarding device).

The sensor signal processing module 121 transmits to the central processing module 122 a signal for maintaining the boarding device as a moving direction and speed information determined from the detection signal of the pressure sensor 113.

As a result, the central processing module 122 outputs a control signal for keeping the boarding device in a stopped state, so that the driving of each driving motor 211 is controlled in a stopped state through the motor control module 123, It will remain stationary.

Next, in order to advance the boarding device, the occupant tilts the handle 114 and the steering frame 112 forward (see FIG. 5B) through the upper body and the hand. At this time, the pressure sensors 113 located relatively to the rear The pressure detected by the pressure sensor is greater than the pressure detected by the pressure sensors located at the front, so that the intention of the passenger to advance the passenger compartment can be accurately grasped.

That is, the sensor signal processing module 121 calculates the two-dimensional pressure distribution from the detection signals of the respective pressure sensors 113, determines the moving direction and the velocity of the boarding device from the calculated two-dimensional pressure distribution, The central processing module 122 outputs a control signal for advancing the boarding device from the signal of the sensor signal processing module 121 and eventually outputs the control signal to the motor control module 123 Controls driving of each driving motor 211 to advance the boarding device.

At this time, the occupant can be set to further increase the advancing speed of the boarding device as the occupant tilts the steering frame 112 forward. For example, when the sensor signal processing module 121 detects the pressure value detected by the front pressure sensors And a speed signal proportional to an average value difference between the pressure values detected by the rear pressure sensors to the central processing module 122. [

Next, the passenger tilts the handle 114 and the steering frame 112 backward through the upper body and the hand (see FIG. 5C), and then the pressure sensors 113 relatively positioned at the front The pressure detected by the pressure sensor is greater than the pressure detected by the pressure sensors located at the rear, so that it is possible to accurately grasp the driver's intention to move the passenger backward.

That is, the sensor signal processing module 121 calculates the two-dimensional pressure distribution from the detection signals of the respective pressure sensors 113, determines the moving direction and the velocity of the boarding device from the calculated two-dimensional pressure distribution, The central processing module 122 outputs a control signal for backing up the boarding device from the signal of the sensor signal processing module 121 and eventually outputs the control signal to the motor control module 123 Controls driving of each driving motor 211 to move the boarding device backward.

At this time, the occupant may be set to further increase the backward speed of the boarding vehicle as the occupant tilts the steering frame 112 rearwardly. For example, when the sensor signal processing module 121 detects the pressure value detected by the front pressure sensors And a speed signal proportional to an average value difference between the pressure values detected by the rear pressure sensors to the central processing module 122. [

Next, the movement of the boarding device with respect to the steering is based on the principle of pulling the handle 114 in the direction opposite to the direction of rotation when the user tilts. When the user tries to make a right turn, the handle on the left side is lifted, The pressure applied to the pressure sensors located on the right side is increased (refer to FIG. 5D), and when the left side is touched, the right side grip is lifted so that the pressure applied to the pressure sensors located on the right side is relatively large The driving intention can be accurately grasped.

Even in this case, the sensor signal processing module 121 calculates the two-dimensional pressure distribution from the detection signals of the respective pressure sensors 113, determines the moving direction and the velocity of the boarding device from the calculated two-dimensional pressure distribution, The central processing module 122 outputs a control signal for turning the boarding device left or right from the signal of the sensor signal processing module 121. As a result, The control module 123 controls the drive of each drive motor 211 to make the boarding device turn left or right.

The following advantages are obtained when the steering control device according to the present invention is applied as described above.

In the conventional one-person stand-up type boarding device, it is difficult to change the direction because the center of gravity is moved through the lower body in a state where the occupant stands and steering operation is performed. However, when the steering control device according to the present invention is applied, It is possible to perform more natural steering control, and consequently, the convenience of the passenger can be increased.

Also, since the person is more familiar with the movement of the upper body than the lower body, the accuracy of the steering can be increased.

It is also possible for disabled persons with uncomfortable legs or hand movements to operate through the movement of the upper body, and can easily adapt to use even in the case of a child or an elderly who lacks the ability to operate.

It is possible to configure the steering apparatus to perform the steering operation through the movement of the upper body by connecting the link device to the shoulder or the end of the obstacle.

The steering control device of the present invention can be applied to various boarding devices in addition to the boarding device shown in FIG. 2, and can be used as a steering control device for a vehicle provided in a driver's seat in a conventional vehicle, , And can also be widely used as a steering control device for a one-passenger small mobile mobile body, a disabled vehicle, a child boarding vehicle, and the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Forms are also included within the scope of the present invention.

100: Steering control device 110: Steering control part
111: fixed frame 111a:
111b: top plate 112: steering frame
113: Pressure sensor 114: Handle
116a, 116b: Support base 120:
121: sensor signal processing module 122: central processing module
123: Motor control module 123: Motor control module
200: boarding device 201: stationary frame
210: front wheel 211: driving motor
212: speed detecting section 220: rear wheel
230: Battery

Claims (6)

A steering control device of a boarding device,
A steering frame fixedly mounted on a fixed frame of the boarding device, a steering frame supported on the fixed frame via the following pressure sensors or supported by the fixed frame so as to be interposed between the fixed frame and the fixed frame, A steering operating part including a plurality of pressure sensors disposed between the fixed frame and the steering frame, and a handle mounted to move the steering frame;
A control unit for outputting a control signal for controlling a moving direction and a speed of the boarding device based on detection signals of the pressure sensors;
And,
Wherein,
A sensor signal processing unit for processing a detection signal of each of the pressure sensors to calculate a two-dimensional pressure distribution applied through a steering frame, determining a moving direction and a speed of the boarding vehicle, A processing module;
A central processing module for outputting a control signal for controlling the moving direction and speed of the boarding device on the basis of the moving direction and the speed information applied from the sensor signal processing module;
And a steering angle sensor for detecting steering angle of the upper body.
delete The method according to claim 1,
Wherein,
Further comprising a motor control module for controlling driving of a driving motor connected to each driving wheel of the boarding device in accordance with a control signal applied from the central processing module,
Wherein the central processing module controls the driving of each driving motor on the basis of the moving direction and the speed information applied by the sensor signal processing module and the speed information inputted from the speed detecting section for detecting the rotational speed of each driving motor. Steering control device of boarding device using motion.
A steering control device of a boarding device,
A steering frame fixedly mounted on a fixed frame of the boarding device, a steering frame supported on the fixed frame via the following pressure sensors or supported by the fixed frame so as to be interposed between the fixed frame and the fixed frame, A steering operating part including a plurality of pressure sensors disposed between the fixed frame and the steering frame, and a handle mounted to move the steering frame;
A control unit for outputting a control signal for controlling a moving direction and a speed of the boarding device based on detection signals of the pressure sensors;
And,
The fixed frame of the steering operation unit is horizontally fixed to the upper portion of the fixed frame of the boarding device. The steering frame is installed below the fixed frame with the pressure sensors interposed therebetween. The handle is installed at the left and right ends of the steering frame And the steering frame can be tilted through the handle as the occupant tilts the upper body with the handle held by both hands.
The method according to claim 1 or 4,
Wherein the handle is installed long before and after the left and right ends of the steering frame so that the handle can be pushed or pulled with the upper body being tilted while being held by the hand of the passenger.
The method according to claim 1 or 4,
Wherein the pressure sensors are constituted by sensors which are divided into front, rear, left and right positions relative to each other.

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