JP7580902B2 - Small electric vehicle - Google Patents

Description

The present invention relates to small electric vehicles such as senior cars and electric wheelchairs, and more specifically to a handle-type electric wheelchair equipped with an obstacle avoidance function.

Small electric vehicles such as senior cars and electric wheelchairs are legally considered pedestrians if they meet regulations regarding speed, vehicle size, etc., and are permitted to travel on sidewalks rather than roadways. As a result, there are various obstacles, such as other pedestrians, on the roadway. As a result, systems have been developed to prevent collisions with pedestrians and other obstacles (see, for example, Patent Document 1).

JP 2016-43111 A

When such small electric vehicles detect an obstacle ahead of the vehicle, they slow down or stop the driving motor to prevent a collision with the obstacle. However, in addition to preventing collisions by slowing down or stopping, systems are also being considered that control the steering motor attached to the steering mechanism to automatically steer the vehicle around obstacles.

However, unlike the autopilot function of automobiles that are designed to drive on roads, the automatic steering in such obstacle avoidance systems is merely a limited function aimed at obstacle avoidance. Therefore, there are cases where the driving route or direction after obstacle avoidance differs from the direction intended by the passenger (operator) of the small electric vehicle, or where the passenger wants to switch to obstacle avoidance through manual steering. Therefore, it is preferable to have an override function that switches to manual steering through the intervention of the passenger during automatic steering for obstacle avoidance.

The present invention has been made in consideration of the above-mentioned shortcomings of the prior art, and its purpose is to provide a small electric vehicle that can properly implement an override function during automatic steering related to obstacle avoidance.

In order to solve the above problems, the present invention provides
A small electric vehicle that can run on sidewalks and can be used as an electric wheelchair,
A steering operation device that steers in response to the operation torque of the left and right handlebars;
an external environment detection unit for detecting a road surface and objects ahead in the traveling direction;
An obstacle avoidance control unit that performs control to automatically avoid the obstacle area by automatically steering in a direction away from the obstacle area when an obstacle area is detected based on detection information from the external environment detection unit,
The obstacle avoidance control unit has an override function that stops automatic steering when an operation torque of a first threshold value or more, which is a forward steering that increases a steering angle in a steering direction of the automatic steering avoidance, is applied to the left and right handles during the automatic steering avoidance, and when an operation torque of a second threshold value or more, which is a reverse steering with respect to the steering direction of the automatic steering avoidance, is applied to the left and right handles during the automatic steering avoidance,
The second threshold value is set to a sufficiently large value so that override by countersteering is prohibited in the early stage of the route travel of the automatic steering avoidance, and is set to a small value so that override by countersteering is permitted in the final stage of the route travel .

As described above, the small electric vehicle according to the present invention has an override function that stops automatic steering when a predetermined operating torque or more that would cause forward steering is applied to the steering wheel during automatic steering avoidance, and when a predetermined operating torque or more that would cause reverse steering is applied to the steering wheel without approaching an obstacle. Therefore, automatic steering can be stopped by manual steering (forward steering) when the passenger recognizes the obstacle and chooses to avoid the obstacle, or when the passenger wants to proceed in the intended direction when moving away from the obstacle by automatic steering avoidance (forward steering, reverse steering), making it possible to avoid the obstacle in a way that reflects the passenger's intention, and automatic steering is continued without immediately being overridden when steering close to the obstacle, preventing approaching the obstacle due to erroneous operation, etc.

1 is a perspective view showing a small electric vehicle according to an embodiment of the present invention; 1 is a side view showing a small electric vehicle according to an embodiment of the present invention. FIG. 2 is a perspective view showing a steering mechanism of the small electric vehicle according to the embodiment of the present invention. FIG. 2 is a plan view showing a handle operation of the small electric vehicle according to the embodiment of the present invention. FIG. 2 is a block diagram showing a control system of the small electric vehicle according to the embodiment of the present invention. 1A is a schematic plan view showing obstacle area detection and FIG. 1B is a schematic plan view showing obstacle avoidance by automatic steering of a small electric vehicle according to a first embodiment of the present invention. 4 is a flowchart showing the operation of the small electric vehicle according to the embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
In Figures 1 and 2, a small electric vehicle 1 according to the first embodiment of the present invention has front wheels 41, which are steered wheels, at the front part 21 of a vehicle body 2, and rear wheels 51, which are drive wheels, at the rear part 23, and the power of a driving motor 5 is transmitted to the rear wheels 51 via a gear box 52.

The vehicle body 2 is equipped with a frame 20 that extends from the front section 21 to the rear section 23, a step 22 is provided between the front section 21 and the rear section 23, and a battery 8 is mounted inside a fairing of the rear section 23. A seat frame 24 is provided on the frame 20 so as to straddle the upper side of the rear section 23, and a seat 3 is supported on a post 30 erected in the center of this seat frame 24.

The seat 3 includes a seat cushion 31, a seat back 32, and armrests 33, 34, and an operating unit 36 is provided at the tip of the right armrest 33 via a support arm 35. The operating unit 36 includes a steering operation device 6 having independent left and right handles 61, 62, and an external environment detection unit 7 including left and right external sensors 71, 72, and accelerators 53, 53 are attached to the left and right handles 61, 62.

The left and right accelerators 53, 53 are connected to a speed controller 50, and the output of the driving motor 5 is controlled by the speed controller 50 in response to the operation of gripping either the left or right accelerator 53, 53 or both, so that the small electric vehicle 1 starts moving, travels at a predetermined speed (or a speed according to the amount of accelerator operation), and stops when the grip of the accelerators 53, 53 is released (the vehicle slows down when the grip is released) and the driver stops.

The steering operation device 6 constitutes a steer-by-wire steering system in which the operation unit consisting of the left and right handlebars 61, 62 and the steering mechanism 4 of the front wheels 41, which are the steered wheels, are not mechanically connected. That is, as shown in FIG. 3, the left and right handlebars 61, 62 have their bases fixed to the rotating shafts of the right steering reaction force actuator 63 and the left steering reaction force actuator 64 (motors), and these rotating shafts are provided with a right operation angle sensor 65 and a left operation angle sensor 66 that detect the operation angles of the handlebars 61, 62, respectively, and a right handlebar torque sensor 67 and a left handlebar torque sensor 68 that detect the torque of each rotating shaft.

The detection signals of the left and right steering angle sensors 65, 66 and the handle torque sensors 67, 68 are sent to the steering controller 60, which outputs corresponding control signals to the steering reaction force actuators 63, 64. While the passenger is steering the left and right handles 61, 62, control signals corresponding to the steering angle and steering torque are output to the steering angle controller 40 of the steering mechanism 4.

For example, as shown in FIG. 4(a), when the vehicle is steered to the left or right (in this case, to the left) and the occupant steers the left and right handlebars 61, 62 in such a way as to increase the operating angle against the steering reaction force of the steering reaction force actuators 63, 64, a control signal corresponding to the operating angle and operating torque is output to the steering angle controller 40 of the steering mechanism 4.

On the other hand, as shown in FIG. 4(b), when the occupant releases the steering force from a state in which the vehicle is steered to the left or right (in this case, to the left), the steering reaction force actuators 63, 64 return the operation angles of the left and right handlebars 61, 62 to zero. The left and right handlebars 61, 62 and the steering reaction force actuators 63, 64 that constitute the steering operation device 6 also serve as vibration means for a vibration warning device that is linked to the obstacle avoidance control unit 11, which will be described later.

The steering mechanism 4 includes knuckles 42 pivoted to the tips of left and right suspension arms 43, and a tie rod 44 connecting the ends of the left and right knuckles 42. In response to a steering angle command from the steering controller 60, the steering angle controller 40 controls the forward and reverse rotation of the steering actuator 46 (motor), and the tie rod 44 moves left or right via the rack and pinion mechanism 45 to steer the front wheels 41, 41 rotatably supported by the left and right knuckles 42. When the rider releases the steering force, the steering actuator 46 returns to a zero steering angle and stops.

Instead of connecting the left and right knuckles 42 with one tie rod 44, a configuration in which a member such as a crank driven by a steering actuator 46 is connected to the left and right knuckles 42 with separate tie rods, or a configuration in which the left and right knuckles 42 are steered by separate steering actuators, may also be used.

The external environment detection unit 7 includes left and right external environment sensors 71, 72 attached to the front end of the operation unit 36, as shown in Fig. 1 and Fig. 2. The external environment sensors 71, 72 are detection means for inputting the presence and relative distance of obstacles, pedestrians, steps, etc. ahead in the direction of travel as image data or point cloud data to the obstacle avoidance control unit 11. For example, a stereo camera or laser radar capable of acquiring the three-dimensional shape of the road surface can be suitably used.

As shown in FIG. 5, the obstacle avoidance control unit 11 includes an obstacle detection unit 12, an obstacle area determination unit 13, an avoidance path generation unit 14, and an alarm control unit 15, and is composed of a computer for implementing these functions, i.e., a ROM that stores programs and data, a CPU that performs calculation processing, a RAM that reads out the programs and data and stores dynamic data and the results of calculation processing, and an input/output interface.

The obstacle detection unit 12 uses image processing such as pattern matching to distinguish between stationary objects such as road surface shapes and buildings ahead in the direction of travel, and moving objects such as pedestrians and bicycles, based on image data and point cloud data acquired by the external environment detection unit 7 (external environment sensors 71, 72). Furthermore, it predicts the future position of a moving object from its current state using a time series filter, and if it estimates the possibility of approaching or contacting the path of the vehicle, it controls the output of the driving motor 5 using the speed controller 50 to decelerate or decelerate and stop the small electric vehicle 1, thereby avoiding a collision or contact.

The obstacle area determination unit 13 detects obstacle areas such as steps (uphill steps, downhill steps), grooves (the allowable width varies depending on the entry angle), narrow sections of the road, and steep slopes (uphill, downhill) where the small electric vehicle 1 cannot travel, from the position information and shape data of stationary objects such as the road surface shape and buildings identified by the obstacle detection unit 12.

The avoidance path generation unit 14 calculates an avoidance path for avoiding the obstacle area detected by the obstacle area determination unit 13 by automatic steering to the right or left based on the road surface shape and position information and shape data of stationary objects such as buildings identified by the obstacle detection unit 12 and the current vehicle position. In other words, it estimates the driving path when a course change is made in the opposite direction to the direction in which the obstacle area ahead is located, and if the driving path can avoid the currently detected obstacle area and does not approach other obstacle areas, it sets the driving path as the avoidance path.

The warning control unit 15 outputs a control signal for a vibration warning to vibration warning devices (steering controller 60, steering reaction force actuators 63, 64) that can operate separately on the left and right sides according to the position of the obstacle area detected by the obstacle area determination unit 13.

In other words, the left and right steering reaction force actuators 63, 64 perform a basic operation of applying a steering reaction force to the left and right handlebars 61, 62 according to the handlebar operation angle of the occupant in response to a control signal from the steering controller 60. In addition, when a vibration alarm is issued, the left or right vibration alarm (control signal) output from the alarm control unit 15 is superimposed on the control signal from the steering controller 60, and the left or right vibration alarm functions as a vibration alarm device that applies minute vibrations to the corresponding handlebars 61, 62.

Next, the obstacle avoidance operation of the small electric vehicle 1 based on the above embodiment will be described with reference to Figures 6 and 7.

While the small electric vehicle 1 is traveling, the external environment detection unit 7 and the obstacle avoidance control unit 11 are always in operation, and the external environment detection unit 7 senses the area ahead in the direction of travel of the small electric vehicle 1 (step 100).

First, the obstacle avoidance control unit 11 (obstacle detection unit 12) detects obstacles such as stationary objects, such as road surface shapes and buildings, and moving objects, such as pedestrians and bicycles, ahead of the vehicle in the direction of travel based on the image data and point cloud data acquired by the external environment detection unit 7 (step 110). If the possibility of contact with a moving object is estimated, the small electric vehicle 1 is decelerated or decelerated to a stop to prevent a collision or contact from occurring.

Next, the obstacle area determination unit 13 detects obstacle areas such as impassable steps (uphill steps, downhill steps), grooves, narrow sections of the road, and steep slopes (uphill, downhill) from the road surface shape and position information and shape data of stationary objects such as buildings identified by the obstacle detection unit 12 (step 120).

For example, as shown in FIG. 6(a), when a downward step D is detected as an obstacle area ahead on the right side in the direction of travel, the warning control unit 15 outputs a "right side" vibration warning (warning control signal) based on the judgment of the obstacle area judgment unit 13, and activates the vibration warning of the right handle 61, so that the passenger can recognize the presence of an obstacle area (downward step D) ahead on the right side in the direction of travel.

In parallel with this, the obstacle avoidance control unit 11 (avoidance path generation unit 14) generates an avoidance path P to avoid the obstacle area (downward step D) by automatic steering in the opposite direction (left direction in this case), as shown in FIG. 6(b), and if there are no other obstacle areas on that path, the driving path is set as the avoidance path P (step 130).

Next, the steering actuator 46 is controlled by the steering angle controller 40 from the obstacle avoidance control unit 11 so that the vehicle travels along the avoidance path P, and obstacle avoidance by automatic steering is started (step 140). At this time, as shown in FIG. 6(b), a vibration alarm is activated on the left handlebar 62 by a control signal from the alarm control unit 15, so that the passenger can recognize that obstacle avoidance by automatic steering to the left has started.

When the vehicle is traveling along the avoidance path P using automatic steering (step 141), the operation angles of the left and right handlebars 61, 62 are controlled to correspond to the steering angle of the front wheels 41', and the left and right handlebar torque sensors 67, 68 detect the operation torques input by manual steering to the corresponding left and right handlebars 61, 62 (step 142).

If a significant steering torque input is detected, it is checked whether the direction of the steering torque is forward steering that increases the steering angle relative to the steering direction of the automatic steering, i.e., whether the input torque of the handle torque sensors 67, 68 is in the positive direction (forward steering) or the negative direction (reverse steering) (step 143).

For example, as shown by symbol P1 in FIG. 6(b), when a positive operating torque resulting in forward steering is detected by either the left or right steering wheel torque sensor 67, 68 at point P1, a check is made to see whether the input torque value is greater than forward steering override threshold 1 (step 144).

If the input torque value is greater than the forward steering override threshold 1, it is determined that the occupant has steered with the intention of switching to manual steering, and obstacle avoidance using automatic steering is terminated and manual steering takes over (step 150). On the other hand, if the input torque value is equal to or less than the forward steering override threshold 1, it is regarded as simply accompanying the operation of gripping the handles 61, 62, and obstacle avoidance using automatic steering continues as is.

On the other hand, if an operating torque that would result in countersteering is detected by either the left or right handle torque sensor 67, 68 at this point P1, a check is made to see whether the input torque value is greater than the countersteering override threshold 2 (step 145).

This countersteering override threshold 2 is set sufficiently large at the beginning of the avoidance path P so that override by countersteering is prohibited. If manual steering is initiated by countersteering at the beginning of the avoidance path P, it is predicted that the vehicle will approach the obstacle area D, so override by countersteering is prohibited and the vehicle continues traveling along the avoidance path P using automatic steering.

After that, for example, as shown by symbol P2 in FIG. 6(b), when an operation torque that results in countersteering is input to either the left or right steering wheel torque sensor 67, 68 at point P2 at the end of the avoidance path P, the operation torque is compared with a later countersteering override threshold value 2 that is set to a value sufficiently smaller than the value at the beginning of the avoidance path P (step 145).

At the end of the avoidance path P (P2), it is expected that the occupant will intervene with steering in order to move from automatic steering along the avoidance path P in the direction originally intended. Therefore, if the input torque value is greater than the later reverse steering override threshold 2, it is determined that the occupant has steered with the intention of switching to manual steering, and obstacle avoidance using automatic steering is terminated, with manual steering taking over (step 150).

If the input torque value is equal to or less than the later reverse steering override threshold 2, the vehicle continues to travel along the route using automatic steering. When the vehicle reaches the end of the avoidance route P (step 141), a vibration alarm (or other notification means) is issued on the left and right handlebars 61, 62 to notify the vehicle of the end of the route using automatic steering, and manual steering takes over (step 150).

The reverse steering override threshold 2 for the early and later stages of route travel can be set to gradually or stepwise decrease according to the route travel distance, or can be set in two stages: in the first half of the route travel (infinity, i.e., override prohibited) and in the second half (a predetermined value), or can be set to be inversely proportional to the route travel distance.

In addition, since a reverse steering override may involve approaching an obstacle area, it is generally preferable to set forward steering override threshold 1 to a value smaller than reverse steering override threshold 2.

In the above embodiment, the override thresholds for forward steering and reverse steering were described regardless of the left and right handles 61, 62. However, in the case of the left and right separate handles 61, 62 in this embodiment, even when steering to the left as shown in FIG. 4(a) (forward steering in FIG. 6(b)), that is, steering to the left around the pivots 61a, 62a of the respective handles 61, 62, the right handle 61 is pushed from the passenger side (extending motion) and the left handle 62 is pulled toward the passenger side (bending motion), and these can be seen as different motions.

In a steer-by-wire steering system, the steering torque is set small enough so that the operation does not become unstable, so excessive steering force is not required, but some research has shown that the maximum force exerted by the upper arm differs between the flexed and extended sides, with the flexed side being greater. Therefore, it is possible to set the override thresholds for the pulling operation (flexion movement) and the pushing operation (extension movement) to different values, for example, the override threshold for the pulling operation (flexion movement) to be higher than the override threshold for the pushing operation (extension movement).

In addition, since the operating force for the pulling operation (bending movement) and the pushing operation (extension movement) may differ depending on the individual conditions of the occupant, such as handedness or reduced physical ability, a measurement program menu for acquiring the individual conditions of the occupant may be prepared in the steering operation device 6 including the left and right handles 61, 62 or the obstacle avoidance control unit 11.

For example, with the small electric vehicle 1 stopped, the left and right handlebars 61, 62 are each pulled (flexed) and pushed (extended) once or several times to obtain basic data on the operating torque, which can then be reflected in the override threshold and the steering reaction force for manual steering, eliminating the influence of the individual conditions of the occupant.

In addition, because steering can be performed using only one of the left and right separate handles 61, 62, steering can be performed in the same way as with an integrated left and right handle or steering wheel, even though the left and right are separate. In addition, the redundancy of having steering systems on both the left and right sides means that even if one of the left and right sides fails, driving can be continued using the other side.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and variations are possible based on the technical concept of the present invention.

REFERENCE SIGNS LIST 1 Small electric vehicle 2 Vehicle body 3 Seat 4 Steering mechanism 5 Travel motor 6 Steering operation device 7 External environment detection unit 11 Obstacle avoidance control unit 12 Obstacle detection unit 13 Obstacle area determination unit 14 Avoidance path generation unit 15 Warning control unit 26, 36 Operation unit 40 Steering angle controller 46 Steering actuator 50 Speed controller 53 Accelerator 60 Steering controller 61, 62 Steering wheel 63, 64 Steering reaction force actuator 65, 66 Operation angle sensor 67, 68 Steering wheel torque sensor 71, 72 External environment sensor

Claims (4)

A small electric vehicle that can run on sidewalks and can be used as an electric wheelchair,
A steering operation device that steers in response to the operation torque of the left and right handlebars;
an external environment detection unit for detecting a road surface and objects ahead in the traveling direction;
An obstacle avoidance control unit that performs control to automatically avoid the obstacle area by automatically steering in a direction away from the obstacle area when an obstacle area is detected based on detection information from the external environment detection unit,
The obstacle avoidance control unit has an override function that stops automatic steering when an operation torque of a first threshold value or more, which is a forward steering that increases a steering angle in a steering direction of the automatic steering avoidance, is applied to the left and right handles during the automatic steering avoidance, and when an operation torque of a second threshold value or more, which is a reverse steering with respect to the steering direction of the automatic steering avoidance, is applied to the left and right handles during the automatic steering avoidance,
The second threshold value is set to a sufficiently large value so that override by countersteering is prohibited in the early stage of the route travel of the automatic steering avoidance, and is set to a small value so that override by countersteering is permitted in the final stage of the route travel . The small electric vehicle according to claim 1, characterized in that the left and right handles are arranged symmetrically and can be steered according to the operating torque that rotates each of them around a rotation axis on the base end side, and the steering operation device can be steered by operating only one of the left and right handles. 3. The small electric vehicle according to claim 2, wherein the first and second threshold values are each greater in a direction in which the left and right handles are pulled toward the passenger than in a direction in which the left and right handles are pushed toward the passenger. 3. The small electric vehicle according to claim 1, wherein the first threshold value is smaller than the second threshold value.

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