JP7700608B2 - Steering control device for electric vehicle - Google Patents

Description

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

Patent Document 1 describes an electric wheelchair in which the left and right drive wheels are driven independently by corresponding motors, and the speed and direction of rotation of the drive wheels are individually controlled to control forward/reverse movement, steering direction, and traveling, and the traveling speed and direction are determined so that the electric wheelchair moves in the direction that the joystick-type control device is operated. In this case, the backward operation of the control device is assigned to a rotation operation at a fixed position, rather than a backward travel.

In recent years, the agricultural producer population has been declining, and there is a demand for mechanization of agricultural work. As part of this effort, there have been attempts to convert electric vehicles such as those described in Patent Document 1 into agricultural vehicles, and such electric vehicles are used to transport harvested products and spray pesticides.

For example, during agricultural harvesting work, a worker loads the harvested crops onto an electric vehicle, and the electric vehicle follows the worker as needed while transporting the crops. This makes work more efficient and reduces the burden on the worker.

At this time, methods for making the electric vehicle follow the worker include using sensors and wired tracking, which is physically connected via wires. With wired tracking, a control wire is connected to the joystick lever of the electric vehicle, and the joystick lever is pulled by the worker via the control wire and falls, causing the vehicle to move using the power of the motor. This method has the advantage of being inexpensive.

JP 2014-64620 A

Wired tracking systems follow the operator well when the control wire is pulled toward the front of the vehicle, but problems can arise when the control wire is pulled to the right or left, or from the left or right to the rear.

The first problem is that when the control wire is pulled directly to the right or left of the electric vehicle, it causes the electric vehicle to make a sharp turn. The other problem is that when the control wire is pulled toward the rear of the electric vehicle, objects on the vehicle may become an obstacle to the control wire, and there is a risk that the direction in which the operator is located will not match the direction in which the joystick lever tilts when pulled by the control wire. Furthermore, when the control wire is pulled toward the rear of the electric vehicle, the electric vehicle may not reverse, but may try to turn the front of the vehicle toward the operator who is at the rear of the vehicle, or may try to reverse in the direction of the pull, turning the front in the opposite direction, resulting in an unstable vehicle posture.

To address this issue, if a cover that covers the joystick lever from the left and right sides to the rear or a stopper that prevents the lever from tilting in a range from the left and right sides to the rear is provided to limit the direction in which the operating wire can indicate the direction of travel for the electric vehicle, this can cause inconvenience when storing the vehicle in a garage or when fine-tuning the vehicle's orientation or position because it cannot be moved left and right or backward.

The present invention aims to provide a steering control device for an electric vehicle that is equipped with a joystick and can prevent sudden turns and stabilize the vehicle's posture when the vehicle is steered by a control wire.

To solve the above problems, the present invention is a steering control device for an electric vehicle having multiple wheels, at least one drive wheel on each side, each drive wheel being driven by a motor, and equipped with a joystick that determines the driving direction depending on the tilt direction, and the joystick is provided with an operation wire connection section, and the vehicle control section is equipped with a mode selector switch that switches between an omnidirectional driving mode in which the electric vehicle drives in the direction in which the joystick is tilted, and a forward driving mode in which the driving of the electric vehicle is restricted when the joystick is tilted in a direction exceeding a predetermined angle to the left or right from the front of the electric vehicle.

In this way, according to the present invention, when operating an electric vehicle equipped with a joystick using an operating wire, it is possible to prevent sudden turns and stabilize the vehicle's posture.

FIG. 1 is a schematic diagram of an electric vehicle according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of setting a predetermined directional range for the tilt direction of a joystick in a forward driving mode of a steering control device for an electric vehicle according to an embodiment of the present invention. FIG. 3 is a flowchart showing a procedure of a mode switching control process of the steering control device for an electric vehicle according to one embodiment of the present invention.

The steering control device for an electric vehicle according to one embodiment of the present invention is a steering control device for an electric vehicle having a plurality of wheels, at least one drive wheel on each side, each drive wheel being driven by a motor, and equipped with a joystick that determines the driving direction depending on the direction in which it is tilted. The joystick is provided with an operating wire connection section, and is configured to include a vehicle control unit that switches between an omnidirectional driving mode in which the electric vehicle drives in the direction in which the joystick is tilted, and a forward driving mode in which the driving of the electric vehicle is restricted when the joystick is tilted in a direction exceeding a predetermined angle left or right from the front of the electric vehicle, depending on the state of a mode selection switch.

As a result, the steering control device for an electric vehicle according to one embodiment of the present invention can prevent sudden turns and stabilize the vehicle posture when steering an electric vehicle equipped with a joystick using an operating wire.

The steering control device for an electric vehicle according to an embodiment of the present invention will be described in detail below with reference to the drawings. The directions of front, rear, left and right used in the description are based on the case where an electric vehicle according to an embodiment of the present invention is moving straight ahead and following, with the direction in which the operator (worker) is located (direction of travel) being defined as forward, the direction opposite to forward being defined as rear, and the left and right direction of the vehicle (vehicle width direction) being defined as left and right.

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

The electric vehicle 1 has multiple wheels (not shown), and has a drive wheel 21 on the right side and a drive wheel 31 on the left side when facing the direction of travel of the electric vehicle 1. The electric vehicle 1 may be rear-wheel drive or front-wheel drive. It may also be all-wheel drive. Regardless of the drive type, in order to improve handling stability and running performance, a steering device (power steering) may be provided on the non-driving wheels, which are the wheels that are not the driving wheels. A steering device (power steering) may also be provided on the driving wheels to change the direction of the driving wheels. By having a steering device, it is possible to use wheels with a larger diameter, which improves running performance in fields, etc.

The right motor 2 rotates using power supplied from a battery (not shown) to drive the right drive wheel 21. The right motor 2 is also connected to the right drive wheel 21 of the electric vehicle 1 via a power transmission mechanism (reduction gear) (not shown) that is composed of multiple gears, etc.

The left motor 3 rotates using power supplied from a battery (not shown) to drive the left drive wheel 31. The left motor 3 is also connected to the left drive wheel 31 of the electric vehicle 1 via a power transmission mechanism (reduction gear) (not shown) that is composed of multiple gears, etc.

The electric vehicle 1 runs using the driving force of the right motor 2 and the left motor 3. In addition, by controlling the rotation direction and rotation speed of the right motor 2 and the left motor 3, the running direction of the electric vehicle 1 can be changed and it can turn. Note that the right motor 2 and the left motor 3 may be in-wheel motors attached to the drive wheels so that the driving force can be transmitted directly to the drive wheels without going through a power transmission mechanism, etc.

The joystick 4 is provided at the front of the vehicle and has a lever (not shown) that extends upward, for example, and the lever can be tilted in either direction from an upright position. 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 of the joystick 4 relative to the electric vehicle 1 (the angle of inclination from the upright position). Furthermore, an operating wire connection section 41 is provided at the tip of the lever to connect an operating wire for remotely operating the lever.

The operating wire is attached to the operating wire connection part 41 via a safety device that will release the operating wire when a large load is applied to the operating wire connection part 41. The safety device is, for example, composed of a locking member that will release when a certain load is applied.

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

The vehicle control unit 8 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input ports, and output ports.

The ROM of this computer unit stores various constants, maps, etc., as well as a program that causes the computer unit to function as the vehicle control unit 8.

In other words, the CPU executes the programs stored in the ROM using the RAM as a working area, and these computer units function as the vehicle control unit 8 in this embodiment.

In addition to the joystick operation signal generator 5 mentioned above, various sensors and switches including the mode change switch 6 are connected to the input port of the vehicle control unit 8.

The mode change switch 6 is a switch that changes the driving mode of the electric vehicle 1, and switches between an "omnidirectional driving mode" described below and a "forward driving mode" that limits the backward driving of the electric vehicle 1. The mode change switch 6 is configured, for example, as a tactile switch, a rocker switch, a toggle switch, or the like, and is operated by the operator who operates the joystick 4.

A contact sensor may be provided on the lever of the joystick 4 to function as a mode changeover switch. In this case, the driving mode of the electric vehicle 1 is changed depending on whether the lever of the joystick 4 is being held or not. In other words, if the mode is changed to "omnidirectional driving mode" when the lever of the joystick 4 is being held, and the joystick 4 is operated directly by the operator without using an operating wire, the electric vehicle 1 is changed to the "omnidirectional driving mode" and can be moved freely left and right or backward, making it easy to store the electric vehicle 1 in a garage or to fine-tune the orientation and position of the electric vehicle 1. The contact sensor may be, for example, a capacitance type touch sensor.

The mode changeover switch may be either the mode changeover switch 6, which is a dedicated switch for simply switching modes, or a contact sensor, or both. When both are provided as mode changeover switches, the mode changeover switch 6 may normally be followed, but when the contact sensor detects contact, the driving mode may be unconditionally switched to "omnidirectional driving mode."

On the other hand, the output port of the vehicle control unit 8 is connected to various control objects including the right motor 2, left motor 3, and forward driving mode display unit 7.

The forward driving mode display unit 7 displays and notifies that the driving mode of the electric vehicle 1 is the forward driving mode described below. The forward driving mode display unit 7 constitutes the notification unit. The forward driving mode display unit 7 is constituted, for example, by an indicator light or the like. The notification unit may be constituted by an alarm that notifies by sound or the like. The forward driving mode is a driving mode that limits the driving direction of the electric vehicle 1 to a specified angle range from the front, and is used when the electric vehicle 1 is to follow the operator. In other words, the forward driving mode display unit 7 indicates that the electric vehicle 1 is being controlled to follow.

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 moves in the direction in which the lever of the joystick 4 is tilted.

The vehicle control unit 8 controls the electric vehicle 1 in an omnidirectional driving mode in which the electric vehicle 1 travels in the direction in which the lever of the joystick 4 is tilted, or in a forward driving mode in which driving is restricted depending on the direction in which the lever of the joystick 4 is tilted. In the forward driving mode, if the lever is within a predetermined angle range to the left or right from the front of the electric vehicle 1, the electric vehicle 1 travels in the direction in which the lever is tilted, and if the lever is tilted in a direction outside the predetermined angle range, the driving of the electric vehicle 1 is restricted. The omnidirectional driving mode and the forward driving mode are switched depending on the state of the mode change switch 6.

In forward driving mode, for example, as shown in FIG. 2, the vehicle control unit 8 drives the electric vehicle 1 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, but does not drive in that direction when the lever of the joystick 4 is tilted in a direction that exceeds α degrees in the left/right direction from the front, which is outside that range.

The predetermined angle is set, for example, to an angle slightly smaller than 90 degrees from the front to the left or right. In other words, when the lever of the joystick 4 is tilted forward, the vehicle control unit 8 causes the electric vehicle 1 to travel in the direction of the tilt. When it is tilted in any other direction, or when the lever of the joystick 4 is tilted in a direction exceeding the predetermined angle, the vehicle control unit 8 does not cause the electric vehicle 1 to travel or turn. In other words, in the forward travel mode, backward travel is restricted or prohibited, and backward travel of the electric vehicle 1 is suppressed.

For example, the vehicle control unit 8 restricts turning when the lever of the joystick 4 is tilted to the left or right. The vehicle control unit 8 may also reduce the driving speed to about one tenth, for example, when the joystick 4 is tilted in a direction outside a predetermined angle range. The vehicle control unit 8 may also accept an operation for a short period of time, for example, about 0.5 seconds, and drive the vehicle, and then stop the vehicle. At this time, if the lever of the joystick 4 is not operated and returns to a neutral state perpendicular to the vehicle body, the vehicle control unit 8 may again accept an operation for a short period of time.

The vehicle control unit 8 may also set the predetermined angle to, for example, 80 degrees or more in both directions from the front and to the left and right, and ignore the operation when the lever of the joystick 4 is tilted in a direction that exceeds the predetermined angle.

The vehicle control unit 8 switches between the omnidirectional driving mode and the forward driving mode only when the lever of the joystick 4 is in a neutral state or when the speed of the electric vehicle 1 is zero. Note that if the mode change switch 6 is switched when the lever of the joystick 4 is not in a neutral state, the vehicle control unit 8 may switch the driving mode when the lever of the joystick 4 is in a neutral state for a certain period of time.

When a contact sensor is provided on the lever of the joystick 4 to serve as a mode changeover switch, the vehicle control unit 8 sets the mode to omnidirectional driving mode while the lever of the joystick 4 is being held and the contact sensor detects contact. When the lever is not being held, the mode is set to forward driving mode, or follows the state of another mode changeover switch.

The mode switching control process performed by the steering control device for an electric vehicle according to this embodiment configured as described above will be described with reference to FIG. 3. The mode switching control process described below is started when the vehicle control unit 8 starts operating, and is executed at preset time intervals.

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

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.

In step S2, the vehicle control unit 8 accepts a change in the driving mode of the electric vehicle 1 by the mode change switch 6. After executing the process of step S2, the vehicle control unit 8 executes the process of step S3. In other words, the vehicle control unit 8 accepts a mode change request requested by operation of the mode change switch 6 only when the electric vehicle 1 is in a stopped state.

The mode switching request can differ depending on the type of mode switch 6. For example, a tactile switch can switch between forward driving mode and omnidirectional driving mode when pressed, or can set a specific driving mode (omnidirectional driving mode) only when pressed. A rocker switch or toggle switch can be switched depending on the state of the mode switch 6, so the operator can directly select between forward driving mode and omnidirectional driving mode.

In step S3, the vehicle control unit 8 determines whether the current driving mode of the electric vehicle 1 is a forward driving mode.

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

In step S4, the vehicle control unit 8 switches the driving mode of the electric vehicle 1 to the omnidirectional driving mode. Thereafter, the vehicle control unit 8 drives the electric vehicle 1 in the direction in which the lever of the joystick 4 is tilted. Then, after executing the process of step S4, the vehicle control unit 8 executes the process of step S5.

In step S5, the vehicle control unit 8 turns off the display by the forward driving mode display unit 7 to stop the display. After executing the process of step S5, the vehicle control unit 8 ends the mode switching control process.

In step S6, the vehicle control unit 8 switches the driving mode of the electric vehicle 1 to a forward driving mode. Thereafter, the vehicle control unit 8 prevents the electric vehicle 1 from driving backward (rearward). Then, after executing the process of step S6, the vehicle control unit 8 executes the process of step S7.

In step S7, the vehicle control unit 8 turns on the display by the forward driving mode display unit 7. After executing the process of step S7, the vehicle control unit 8 ends the mode switching control process.

In this way, in this embodiment, the vehicle control unit 8 switches between an omnidirectional driving mode in which the electric vehicle 1 travels in the direction in which the lever of the joystick 4 is tilted, and a forward driving mode in which, when the lever of the joystick 4 is tilted in a direction that exceeds a predetermined angle to the left or right from the front of the electric vehicle 1, the driving of the electric vehicle 1 is restricted in that direction, depending on the input state of the mode changeover switch 6.

As a result, when the joystick 4 is operated by connecting an operating wire to the tip of the lever, the forward driving mode can be set to prevent the electric vehicle 1 from making sharp turns or from moving in an unintended direction due to on-board objects interfering with the operating wire, thereby stabilizing the vehicle posture.

On the other hand, when parking or stopping or fine-tuning the vehicle position, the omnidirectional driving mode allows for better maneuverability and easier driving. The joystick 4 is provided in front of the electric vehicle 1 so that on-board objects do not interfere with the operating wire when following, and the mode changeover switch 6 is provided in front of the electric vehicle 1 near the joystick 4 and positioned so that it can be operated simultaneously with the joystick 4. A protective member may be provided on the mode changeover switch 6 to prevent it from being pressed accidentally.

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 1, and when the lever of the joystick 4 is tilted in a direction from the front to the left/right direction that exceeds the predetermined angle, the vehicle control unit 8 does not drive or turn the electric vehicle 1 in that direction. In other words, when the lever of the joystick 4 is tilted in a directional range from the side to the rear, the electric vehicle 1 does not drive or turn in that direction.

This allows for more strict restrictions on lateral and backward driving, limiting driving to forwards only, improving safety compared to omnidirectional driving mode.

The vehicle also includes a mode changeover switch 6 that is operated by the operator to request the intended driving mode, and a forward driving mode display unit 7 that indicates that the driving mode of the electric vehicle 1 is forward driving mode.

This allows the operator to easily change the driving mode of the electric vehicle 1 and easily know the driving mode of the electric vehicle 1, thereby preventing unintended starting, etc.

In addition, the vehicle control unit 8 switches between the omnidirectional driving mode and the forward driving mode using the mode change switch 6 only when the lever of the joystick 4 is in the neutral state.

By prohibiting mode changes while the joystick 4 is being operated, unintended starting or stopping can be prevented. For example, when the joystick 4 is operated backward in forward driving mode and the mode change switch 6 is used to switch to omnidirectional driving mode, unintended starting can be prevented.

In addition, a contact sensor is provided on the lever of the joystick 4, and the vehicle control unit 8 can set the driving mode of the electric vehicle 1 to the omnidirectional driving mode while the contact sensor detects contact.

This allows the driving mode of the electric vehicle 1 to be changed to omnidirectional driving mode simply by gripping the lever of the joystick 4, thereby improving convenience.

In addition, the operating wire connection section 41 is equipped with a safety device that activates when a large load is applied.

When the operating wire is pulled more than necessary, it can be prevented from coming off the lever of the joystick 4 and damaging the joystick 4. In addition, by providing an extension mechanism on the operating wire side, it is possible to provide flexibility in the distance between the operator and the electric vehicle 1. Furthermore, if the extension mechanism is equipped with a spring-loaded winding device, it is possible to make the electric vehicle 1 follow the operator's work without interfering with the operator's work operations.

In this embodiment, an example has been described in which the vehicle control unit 8 performs various determinations and calculations based on various sensor information, but the present invention is not limited to this. The electric vehicle 1 may have a communication unit capable of communicating with an external device such as an external server, and the external device may perform various determinations and calculations based on the detection information of the various sensors transmitted from the communication unit. The communication unit may receive the determination results and calculation results, and the received determination results and calculation results may be used to perform various controls.

Although an embodiment of the present invention has been disclosed, it is apparent that modifications may be made by one of ordinary skill in the art without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Electric vehicle 2 Right motor (motor)
3 Left motor (motor)
4 Joystick 5 Joystick operation signal generating unit 6 Mode changeover switch 7 Forward driving mode display unit (notification unit)
8 Vehicle control unit 21, 31 Drive wheel 41 Operation wire connection unit

Claims (6)

A steering control device for an electric vehicle having a plurality of wheels, at least one drive wheel on each of the left and right sides, each drive wheel being driven by a motor, and equipped with a joystick that determines a traveling direction depending on a tilt direction of the drive wheels,
The joystick is provided with an operation wire connection portion,
A steering control device for an electric vehicle that includes a vehicle control unit that switches between an omnidirectional driving mode in which the electric vehicle travels in the direction the joystick is tilted, and a forward driving mode in which the driving of the electric vehicle is restricted when the joystick is tilted in a direction exceeding a predetermined angle to the left or right from the front of the electric vehicle, depending on the state of a mode selector switch. the predetermined angle in the forward traveling mode is set to an angle slightly smaller than 90 degrees in the left/right direction from the front of the electric vehicle,
The steering control device for an electric vehicle according to claim 1 , wherein the vehicle control unit does not cause the electric vehicle to travel or turn when the joystick is tilted in a direction exceeding the predetermined angle. The steering control device for an electric vehicle according to claim 1 or 2, further comprising an externally operated switch as the mode changeover switch, and a notification unit that notifies the driver that the driving mode of the electric vehicle is the forward driving mode. The steering control device for an electric vehicle according to claim 3, wherein the vehicle control unit switches between the omnidirectional driving mode and the forward driving mode using the mode change switch only when the joystick is in a neutral state. A contact sensor is provided on the joystick;
4. The steering control device for an electric vehicle according to claim 2, wherein the vehicle control unit sets the driving mode of the electric vehicle to the omnidirectional driving mode while the contact detection sensor detects a contact. The steering control device for an electric vehicle according to any one of claims 1 to 5, wherein the operating wire connection section is provided with a safety device that operates when a large load is applied.

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