Steering control device for an electric vehicle

Abstract

To provide a steering control device of an electric vehicle capable of stabilizing a vehicle posture while preventing sharp turn when steering the electric vehicle equipped with a joy stick by an operation wire.SOLUTION: A steering control device of an electric vehicle includes a right motor 2 driving a right driving wheel 21, a left motor 3 driving a left driving wheel 31, a joy stick 4 determining a traveling direction according to the tilted direction, a mode switch 6 for switching between an omnidirectional traveling mode for causing an electric vehicle 1 to travel in a direction to which the joy stick 4 is tilted and a forward traveling mode for restricting the traveling of the electric vehicle 1 when the joy stick 4 is tilted in a direction exceeding a predetermined angle in the lateral direction from the front of the electric vehicle 1, and a vehicle control unit 8 for switching between the omnidirectional traveling mode and the forward traveling mode according to the state of the mode switch 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a steering control device for an electric vehicle.

Background Art

[0002] Patent Document 1 discloses an electric wheelchair that controls forward and backward movement, steering direction, and traveling by independently driving left and right drive wheels with corresponding motors and individually controlling the speed and direction of rotation of the drive wheels, and determines the traveling speed and direction so that the wheelchair moves in the direction in which an operator of a joystick-type operating means operates. It is described that a rotational movement at a fixed position is assigned to an operation to the rear of this operator instead of backward traveling.

[0003] By the way, in recent years, the population of producers in agriculture has been decreasing, and mechanization of work has been demanded. As part of this, there have been attempts to divert electric vehicles such as those described in Patent Document 1 to agricultural vehicles, and such electric vehicles are used for transporting harvested crops and spraying chemicals.

[0004] For example, in the work of harvesting agricultural crops, an operator appropriately loads the harvested agricultural crops onto an electric vehicle, and the electric vehicle appropriately follows the operator while transporting the agricultural crops. Thereby, work efficiency can be improved and the load can be reduced.

[0005] At this time, as a method of making an electric vehicle follow an operator, there are a method using a sensor and a method such as a wired following type that is physically connected by a wire or the like. The wired following type connects an operation wire or the like to a lever of a joystick of an electric vehicle, and the vehicle travels by the force of a motor when the lever of the joystick is pulled and tilted by the operator through the operation wire or the like. This method is excellent in terms of being inexpensive.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the case of a wired tracking type, although it often follows the operator when pulling the operation wire in front of the vehicle, problems may occur when pulling the operation wire to the right or left, and from the right and left to the rear.

[0008] The first problem is that when the operation wire is pulled directly to the right or left side of the electric vehicle, the electric vehicle makes a sharp turn. Another problem is that when pulling the operation wire to the rear of the electric vehicle, the on-vehicle load may become an obstacle to the operation wire, and there is a possibility that the direction in which the operator is located does not match the direction in which the lever of the joystick that is pulled by the operation wire tilts. Furthermore, when pulling the operation wire to the rear of the electric vehicle, the electric vehicle may try to turn the front part in the reverse direction when it tries to face the front of the vehicle toward the operator behind the vehicle without backing up or when it tries to back up in the pulled direction, so the vehicle posture is not stable.

[0009] As a countermeasure against such problems, when a cover that covers the rear from the left and right sides of the lever of the joystick or a stopper is provided so that the lever cannot tilt in the direction range from the left and right sides to the rear to limit the indicated direction by the operation wire regarding the traveling direction of the electric vehicle, it becomes inconvenient when storing the vehicle in the garage or when finely adjusting the direction and position of the vehicle because it cannot be moved to the left, right, or rear.

[0010] Therefore, an object of the present invention is to provide a steering control device for an electric vehicle that can prevent sharp turning and the like and stabilize the vehicle posture when operating an electric vehicle equipped with a joystick with an operation wire.

Means for Solving the Problems

[0011] To solve the above problems, the present invention provides a steering control device for an electric vehicle having a plurality of wheels, at least one driving wheel on each of the left and right sides, each of the driving wheels being driven by a motor, and comprising a joystick for determining the traveling direction according to the tilted direction, wherein an operation wire connection part is provided on the joystick, and a vehicle control unit is provided for switching between an omnidirectional traveling mode in which the electric vehicle travels in the direction in which the joystick is tilted and a forward traveling mode in which the traveling of the electric vehicle is restricted when the joystick is tilted in a direction exceeding a predetermined angle in the left-right direction from the front of the electric vehicle according to the state of a mode switching switch.

Advantages of the Invention

[0012] Thus, according to the present invention, when operating an electric vehicle equipped with a joystick with an operation wire, it is possible to prevent sudden turning and stabilize the vehicle posture.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0014] The steering control device for an electric vehicle according to an embodiment of the present invention is a steering control device for an electric vehicle having a plurality of wheels, at least one driving wheel on each of the left and right sides, each driving wheel being driven by a motor, and including a joystick for determining the traveling direction according to the tilted direction, wherein an operation wire connection part is provided on the joystick, and a vehicle control unit is provided which switches between an omnidirectional traveling mode in which the electric vehicle travels in the direction in which the joystick is tilted and a forward traveling mode in which the traveling of the electric vehicle is restricted when the joystick is tilted in a direction exceeding a predetermined angle in the left-right direction from the front of the electric vehicle according to the state of a mode switching switch.

[0015] Accordingly, when operating an electric vehicle equipped with a joystick with an operation wire, the steering control device for an electric vehicle according to an embodiment of the present invention can prevent sharp turning and the like and stabilize the vehicle posture.

Example

[0016] Hereinafter, with reference to the drawings, the steering control device for an electric vehicle according to an embodiment of the present invention will be described in detail. The front, rear, left, and right directions used in the description are based on the time when the electric vehicle according to an embodiment of the present invention travels straight and follows, with the direction in which the operator (worker) is located (traveling direction) being the front, the opposite direction of the front being the rear, and the left-right direction (vehicle width direction) of the vehicle being the left-right direction.

[0017] In FIG. 1, an electric vehicle 1 equipped with the steering control device for an electric vehicle according to an embodiment of the present invention includes a right motor 2, a left motor 3, a joystick 4, and a joystick operation signal generation unit 5.

[0018] The electric vehicle 1 has a plurality of wheels (not shown), has a drive wheel 21 on the right side and a drive wheel 31 on the left side in the traveling direction of the electric vehicle 1. The electric vehicle 1 may be rear-wheel drive, front-wheel drive, or all-wheel drive. Also, regardless of the drive type, a steering device (power steering) may be provided for the driven wheels, which are wheels that are not drive wheels, in order to improve handling stability and ride comfort. A steering device (power steering) may also be provided for the drive wheels to change the direction of the drive wheels. By having a steering device, it becomes possible to use wheels with a large diameter, improving the ride comfort on fields and the like.

[0019] The right motor 2 rotates by the electric power supplied from a battery (not shown) and drives the right drive wheel 21. Also, the right motor 2 is connected to the right drive wheel 21 of the electric vehicle 1 via a power transmission mechanism (speed reducer, not shown) composed of a plurality of gears and the like.

[0020] The left motor 3 rotates by the electric power supplied from a battery (not shown) and drives the left drive wheel 31. Also, the left motor 3 is connected to the left drive wheel 31 of the electric vehicle 1 via a power transmission mechanism (speed reducer, not shown) composed of a plurality of gears and the like.

[0021] The electric vehicle 1 travels by the driving forces of the right motor 2 and the left motor 3. Also, by controlling the rotation direction and rotation speed of the right motor 2 and the left motor 3, the traveling direction of the electric vehicle 1 can be changed or it can be made to turn. Note that the right motor 2 and the left motor 3 may be in-wheel motors attached to the drive wheels such that they can directly transmit the driving force to the drive wheels without passing through a power transmission mechanism or the like.

[0022] The joystick 4 is provided in front of the vehicle and has, for example, a lever (not shown) provided to extend upward. The lever can be tilted in any direction from the upright state. The electric vehicle 1 is controlled to move in the direction in which the lever of the joystick 4 is tilted, and the driving force is adjusted according to the tilt angle (the angle of tilt from the upright state) of the joystick 4 with respect to the electric vehicle 1. Further, an operation wire connection portion 41 for connecting an operation wire for remotely operating the lever is provided at the tip of the lever.

[0023] The operation wire is attached to the operation wire connection portion 41 via a safety device such that the operation wire comes off when a large load is applied to the operation wire connection portion 41. The safety device is composed of, for example, a locking member that comes off at a certain load.

[0024] The joystick operation signal generation unit 5 outputs a signal corresponding to the direction and tilt angle in which the lever of the joystick 4 is tilted to the vehicle control unit 8.

[0025] The vehicle control unit 8 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an input port, and an output port.

[0026] In the ROM of this computer unit, a program for causing the computer unit to function as the vehicle control unit 8 is stored together with various constants, various maps, and the like.

[0027] That is, when the CPU executes the program stored in the ROM using the RAM as a work area, these computer units function as the vehicle control unit 8 in this embodiment.

[0028] In addition to the aforementioned joystick operation signal generation unit 5, various sensors and switches including a mode changeover switch 6 are connected to the input port of the vehicle control unit 8.

[0029] The mode switching switch 6 is a switch for switching the running mode of the electric vehicle 1, and switches between the "omnidirectional running mode" described later and the "forward running mode" that restricts the running of the electric vehicle 1 backward. The mode switching switch 6 is constituted by, for example, a tactile switch, a rocker switch, a toggle switch, etc., and is operated by an operator who operates the joystick 4.

[0030] Note that a contact sensing sensor may be provided on the lever of the joystick 4 to serve as a mode switching switch. In this case, the running mode of the electric vehicle 1 is switched according to whether or not the lever of the joystick 4 is being held. That is, when the lever of the joystick 4 is being held and it is switched to the "omnidirectional running mode", when the joystick 4 is directly operated by the operator without using an operation wire, the electric vehicle 1 can be switched to the "omnidirectional running mode" and freely moved left, right, or backward, and it is easy to store the electric vehicle 1 in a garage or finely adjust the orientation and position of the electric vehicle 1. The contact sensing sensor is constituted by, for example, a capacitance type touch sensor or the like.

[0031] As the mode switching switch, either the mode switching switch 6 which is a dedicated switch for simply switching the mode or the contact sensing sensor may be provided, or both may be provided. When both are provided as the mode switching switch, usually following the mode switching switch 6, when the contact sensing sensor senses contact, the running mode may be unconditionally switched to the "omnidirectional running mode".

[0032] On the other hand, in addition to the aforementioned right motor 2 and left motor 3, various control targets including the forward running mode display unit 7 are connected to the output port of the vehicle control unit 8.

[0033] The forward travel mode display unit 7 displays and notifies that the travel mode of the electric vehicle 1 is the forward travel mode described later. The forward travel mode display unit 7 constitutes a notification unit. The forward travel mode display unit 7 is composed of, for example, an indicator light or the like. It may also be composed of an alarm or the like that notifies with sound as the notification unit. The forward travel mode is a travel mode that restricts the travel direction of the electric vehicle 1 to a predetermined angular range from the front, and is used when making the electric vehicle 1 follow the operator. That is, the forward travel mode display unit 7 displays that the electric vehicle 1 is performing follow-up control.

[0034] In this embodiment, the vehicle control unit 8 controls the right motor 2, the left motor 3, etc. based on the signal output by the joystick operation signal generation unit 5 so that the electric vehicle 1 travels in the direction in which the lever of the joystick 4 is tilted.

[0035] The vehicle control unit 8 controls the electric vehicle 1 in the omnidirectional travel mode in which the electric vehicle 1 travels in the direction in which the lever of the joystick 4 is tilted, or in the forward travel mode in which the travel is restricted depending on the direction in which the lever of the joystick 4 is tilted. In the forward travel mode, if the lever is within a predetermined angular range in the left-right direction from the front of the electric vehicle 1, the electric vehicle 1 travels in the direction in which the lever is tilted, and when the lever is tilted in a direction outside the predetermined angular range, the travel of the electric vehicle 1 is restricted. The omnidirectional travel mode and the forward travel mode are switched according to the state of the mode switch 6.

[0036] In the forward travel mode, the vehicle control unit 8, for example, as shown in FIG. 2, causes the electric vehicle 1 to travel in the direction in which the lever is tilted within a range of α degrees or less in the left-right direction from the front of the electric vehicle 1, and when the lever of the joystick 4 is tilted in a direction exceeding α degrees in the left-right direction from the front outside the range, the vehicle does not travel in that direction.

[0037] As the predetermined angle, for example, the angle from the front to the left - right direction is set to be slightly less than 90 degrees. That is, when the lever of the joystick 4 is tilted forward, the vehicle control unit 8 causes the electric vehicle 1 to travel in the tilted direction. When tilted in other directions, or when the lever of the joystick 4 is tilted in a direction exceeding the predetermined angle, the vehicle control unit 8 does not perform the running or turning of the electric vehicle 1. That is, in the forward - running mode, the backward running is restricted or prohibited, suppressing the running of the electric vehicle 1 to the rear side.

[0038] For example, when the lever of the joystick 4 is tilted leftward or rightward, the vehicle control unit 8 restricts turning. Also, when the tilt operation is performed in a direction outside the predetermined angle range, the vehicle control unit 8 may, for example, reduce the driving speed to about one - tenth. Also, the vehicle control unit 8 may, for example, accept the operation for only a short time of about 0.5 seconds to perform running and then stop. At this time, when the lever of the joystick 4 returns to the neutral state perpendicular to the vehicle body without being operated, it may also accept the operation for only a short time.

[0039] Also, as the predetermined angle, for example, the vehicle control unit 8 sets an angle of 80 degrees or more from the front to the left - right directions respectively, and when the lever of the joystick 4 is tilted in a direction exceeding the predetermined angle, the operation may be ignored.

[0040] The vehicle control unit 8 switches between the omnidirectional running mode and the forward - running mode only when the lever of the joystick 4 is in the neutral state or when the speed of the electric vehicle 1 is zero. Note that when the mode - change switch 6 is switched when the lever of the joystick 4 is in a state other than the neutral state, the vehicle control unit 8 may perform the switching of the running mode when the lever of the joystick 4 has been in the neutral state for a certain period of time.

[0041] When the vehicle control unit 8 uses a contact sensor provided on the lever of the joystick 4 as a mode changeover switch, it sets the omnidirectional driving mode while the lever of the joystick 4 is being gripped and the contact sensor senses the contact. When the lever is not being gripped, it sets the forward driving mode, or follows the state of other mode changeover switches.

[0042] Regarding the mode change control process by the steering control device of the electric vehicle according to this embodiment configured as described above, it will be described with reference to FIG. 3. Note that the mode change control process described below starts when the vehicle control unit 8 starts operating and is executed at a preset time interval.

[0043] In step S1, the vehicle control unit 8 determines whether the speed of the electric vehicle 1 is zero.

[0044] If it is determined that the speed of the electric vehicle 1 is zero, the vehicle control unit 8 executes the process of step S2. If it is determined that the speed of the electric vehicle 1 is not zero, the vehicle control unit 8 executes the process of step S1.

[0045] In step S2, the vehicle control unit 8 accepts the switching of the driving mode of the electric vehicle 1 by the mode changeover switch 6. After executing the process of step S2, the vehicle control unit 8 executes the process of step S3. That is, the vehicle control unit 8 accepts the mode change request required by the operation of the mode changeover switch 6 only when the electric vehicle 1 is in a stopped state.

[0046] Note that the switching request for this mode can be made different depending on the type of the mode switch 6. For example, in the case of a tactile switch, when a pressing operation is performed, the forward travel mode and the omnidirectional travel mode can be switched to a mode different from the current travel mode, or alternatively, only when the pressing operation is being performed, a specific travel mode (omnidirectional travel mode) can be set. In the case of a rocker switch or a toggle switch, since it can be switched according to the state of the mode switch 6, the operator can directly select the forward travel mode and the omnidirectional travel mode.

[0047] In step S3, the vehicle control unit 8 determines whether the current travel mode of the electric vehicle 1 is the forward travel mode.

[0048] If it is determined that the current travel mode of the electric vehicle 1 is the forward travel mode, the vehicle control unit 8 executes the process of step S4. If it is determined that the current travel mode of the electric vehicle 1 is not the forward travel mode, the vehicle control unit 8 executes the process of step S6.

[0049] In step S4, the vehicle control unit 8 switches the travel mode of the electric vehicle 1 to the omnidirectional travel mode. Thereafter, the vehicle control unit 8 makes the electric vehicle 1 travel in the direction in which the lever of the joystick 4 is tilted. And after executing the process of step S4, the vehicle control unit 8 executes the process of step S5.

[0050] In step S5, the vehicle control unit 8 turns off the display by the forward travel mode display unit 7 and stops the display. After executing the process of step S5, the vehicle control unit 8 ends the mode switching control process.

[0051] In step S6, the vehicle control unit 8 switches the travel mode of the electric vehicle 1 to the forward travel mode. Thereafter, the vehicle control unit 8 suppresses the travel of the electric vehicle 1 to the rear side (rear). And after executing the process of step S6, the vehicle control unit 8 executes the process of step S7.

[0052] In step S7, the vehicle control unit 8 turns on the display by the forward travel mode display unit 7 and causes it to be displayed. After executing the process of step S7, the vehicle control unit 8 ends the mode switching control process.

[0053] As described above, in this embodiment, the vehicle control unit 8 switches between the omnidirectional travel mode in which the electric vehicle 1 travels in the direction in which the lever of the joystick 4 is tilted and the forward travel mode in which the travel of the electric vehicle 1 in the direction in which the lever of the joystick 4 is tilted from the front of the electric vehicle 1 beyond a predetermined angle in the left-right direction is restricted, according to the input state of the mode switching switch 6.

[0054] Thereby, when an operation wire is connected to the tip of the lever of the joystick 4 and operated, by setting the forward travel mode, it is possible to prevent the electric vehicle 1 from making a sharp turn or the on-vehicle load from interfering with the operation wire and causing the electric vehicle 1 to move in an unintended direction, and to stabilize the vehicle posture.

[0055] On the other hand, when parking or finely adjusting the vehicle position, by setting the omnidirectional travel mode, it is possible to make small turns well and drive easily. The joystick 4 is provided in front of the electric vehicle 1 so that the on-vehicle load does not interfere with the operation wire during following, and the mode switching switch 6 is provided in front of the electric vehicle 1 in the vicinity of the joystick 4 and arranged at a position where it can be operated simultaneously with the joystick 4. Note that a protection member may be provided for the mode switching switch 6 so as not to be accidentally pressed.

[0056] Also, the predetermined angle in the forward travel mode is set to an angle slightly smaller than 90 degrees in the left-right direction from the front of the electric vehicle 1, and when the lever of the joystick 4 is tilted in a direction exceeding the predetermined angle in the left-right direction from the front, the vehicle control unit 8 does not cause the electric vehicle 1 to travel or turn in that direction. That is, when the lever of the joystick 4 is tilted in the direction range from the side to the rear side, the electric vehicle 1 does not travel or turn in that direction.

[0057] By doing so, traveling in the lateral or rearward directions can be more severely restricted and limited to traveling forward, thereby enhancing safety compared to the omnidirectional traveling mode.

[0058] Furthermore, a mode switching switch 6 is provided as a mode switching switch for the operator to operate and request the intended traveling mode, and a forward traveling mode display unit 7 for displaying that the traveling mode of the electric vehicle 1 is the forward traveling mode is provided.

[0059] Thereby, the operator can easily change the traveling mode of the electric vehicle 1, can easily know the traveling mode of the electric vehicle 1, and can suppress unintended starting and the like.

[0060] In addition, the vehicle control unit 8 performs switching between the omnidirectional traveling mode and the forward traveling mode by the mode switching switch 6 only when the lever of the joystick 4 is in the neutral state.

[0061] By prohibiting mode changes during the operation of the joystick 4, unintended starting and stopping can be suppressed. For example, when the joystick 4 is being operated rearward during the forward traveling mode and is switched to the omnidirectional traveling mode by the mode switching switch 6, unintended starting can be suppressed.

[0062] In addition, a contact sensing sensor is provided on the lever of the joystick 4, and the vehicle control unit 8 can set the traveling mode of the electric vehicle 1 to the omnidirectional traveling mode while the contact sensing sensor senses contact.

[0063] Thereby, the traveling mode of the electric vehicle 1 can be set to the omnidirectional traveling mode simply by gripping the lever of the joystick 4, enhancing convenience.

[0064] In addition, the operation wire connection part 41 is provided with a safety device that operates when a large load is applied.

[0065] When the operating wire is pulled more than necessary, the operating wire can be detached from the lever of the joystick 4 so that the joystick 4 is not damaged. Note that a telescopic mechanism can be provided on the operating wire side to give freedom to the distance between the operator and the electric vehicle 1. Furthermore, if it is a telescopic mechanism equipped with a spring-biased winding device, it can follow the running without interfering with the operator's work operation.

[0066] In this embodiment, an example in which the vehicle control unit 8 makes various determinations and calculations based on various sensor information has been described. However, the present invention is not limited to this. The electric vehicle 1 is provided with a communication unit capable of communicating with an external device such as an external server. Various determinations and calculations may be performed by the external device based on the detection information of various sensors transmitted from the communication unit, and the determination result and calculation result are received by the communication unit, and various controls may be performed using the received determination result and calculation result.

[0067] Although embodiments of the present invention have been disclosed, it is obvious that those skilled in the art can make changes without departing from the scope of the present invention. It is intended that all such modifications and equivalents be included in the following claims.

Explanation of Signs

[0068] 1 Electric vehicle 2 Right motor (motor) 3 Left motor (motor) 4 Joystick 5 Joystick operation signal generation unit 6 Mode switch 7 Forward travel mode display unit (notification unit) 8 Vehicle control unit 21, 31 Driving wheels 41 Operating wire connection part

Claims

1. A steering control device for an electric vehicle having a plurality of wheels, at least one driving wheel on each of the left and right sides, each of the driving wheels being driven by a motor, and comprising a joystick for determining a traveling direction according to a tilted direction, wherein an operation wire connection part is provided on the joystick, the vehicle control unit includes an omnidirectional driving mode for driving the electric vehicle in the direction in which the joystick is tilted, and a forward driving mode for restricting the driving of the electric vehicle when the joystick is tilted in a direction exceeding a predetermined angle in the left-right direction from the front of the electric vehicle, and the vehicle control unit switches between the modes according to the state of a mode switching switch.

2. The predetermined angle in the forward driving mode is set to an angle slightly smaller than 90 degrees in the left-right direction from the front of the electric vehicle, and the vehicle control unit according to claim 1, wherein when the joystick is tilted in a direction exceeding the predetermined angle, the electric vehicle does not travel or turn.

3. The steering control device for an electric vehicle according to claim 1 or claim 2, comprising an externally operable switch as the mode switching switch, and a notification unit for notifying that the traveling mode of the electric vehicle is the forward driving mode.

4. The vehicle control unit according to claim 3, switches between the omnidirectional driving mode and the forward driving mode by the mode switching switch only when the joystick is in a neutral state.

5. A contact sensing sensor is provided on the joystick, and the vehicle control unit according to claim 2 or claim 3, wherein while the contact sensing sensor senses contact, the traveling mode of the electric vehicle is set to the omnidirectional driving mode.

6. The operation wire connection part according to any one of claims 1 to 5, is provided with a safety device that operates when a large load is applied.

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