KR20210041234A - Driving control system for electrical wheelchair - Google Patents

Abstract

The present invention relates to an electric wheelchair driving control system with improved straight driving performance comprising: a control signal generator for generating a drive or turn signal of an electric wheelchair which is accelerated or decelerated through a low pass filter (LPF) after receiving an operation signal of a joystick; and a motor controller having a dynamics model setting part to which a disturbance observer (DOB) is applied and a speed controller based on a yaw moment observer (YMO) to control driving of a motor using a signal of the control signal generator. Therefore, driving is controlled according to a straight direction dynamics model and a rotational direction dynamics model, set by the dynamics model setting part, and a parameter, set by the speed controller.

Description

Driving control system for electrical wheelchair with improved straightness driving ability

The present invention relates to an electric wheelchair travel control system with improved straight travel performance.

In general, wheelchairs are classified into manual and electric types, and the manual type is a wheelchair that moves by the power of a guardian or user, and the electric type is a wheelchair that controls the speed by driving a general DC drive motor or a BLDC (BrushLess DC) driven motor with the power of a storage battery. to be.

In the electric wheelchair, the direction and speed are controlled by transmitting information of the direction and speed to the wheelchair control CPU by a joystick, which is a user's manipulator. That is, the electric wheelchair is characterized in that the front, rear, left and right directions and speeds are controlled with a joystick, and the user controls the joystick for the set direction and speed, and travels with a speed proportional to the tilt of the joystick in a desired direction. .

A general electric wheelchair is braked at a stop braking with a set braking force irrespective of the slope of the road, and when the user only changes the speed through continuous driving, the driving motor accelerates and decelerates according to the angle of the joystick. In addition, in the electric wheelchair, when the user wants to turn the direction, the joystick is switched from the front-rear direction to the left-right direction, or according to the operation of switching from the left-right direction to the front-rear direction.

As described above, the electric wheelchair can be easily controlled by a user with a simple operation using a joystick, and driving, turning, and braking can be easily controlled, providing innovative convenience compared to a manual wheelchair.

In the control of the electric wheelchair, in an ideal condition (indoor environment) where the ground is flat without irregularities or inclinations, straight forward, backward, and direction change can be accurately controlled while driving. However, in a realistic situation such as an outdoor environment, not only the ground surface is not ideally flat, and dangerous factors such as irregularities and slopes always exist. Electric wheelchairs running in outdoor environments are instantaneous when passing through a concave or inclined place, or when the user's center of gravity is shifted to one side, the center of the wheelchair is disturbed and the direction of the wheelchair is changed, resulting in a sudden drop in straight driving performance. As a result, it is often issued that the user proceeds in a direction different from the intended direction, causing a great risk. Therefore, in an electric wheelchair, there is a strong need to supplement the performance of straight forward and backward driving and the accuracy of direction change even in an environment with fine irregularities or an incline and a condition in which the user's center of gravity is shifted to the left or right. .

In addition, in the conventional electric wheelchair, a signal generated by operation of a joystick during acceleration or deceleration is transmitted to the wheel through a drive motor.A discontinuous pattern is detected during acceleration and deceleration using a joystick, so that the user does not respond quickly to acceleration and deceleration. There is a problem that cannot be done. This discontinuous acceleration and deceleration pattern also appears when the electric wheelchair is switched from a straight motion to a turning motion or from a turning motion to a straight motion.

In addition, a conventional electric wheelchair includes a joystick and a function button. The function button unit includes a plurality of buttons for various functions such as on-off and driving mode, and the user must operate to press the function button separately from the joystick for on-off operation of the electric wheelchair and selection of driving mode. The pressing operation of such a function button can be easily operated from the standpoint of a general person, but there is a problem in that a user with a physical discomfort has difficulty in manipulating the function button.

The present invention has been proposed in order to solve the above problems, and an object of the present invention is to provide an electric wheelchair driving control system capable of stably driving straight ahead without being disturbed even when the ground surface is uneven outdoors.

In addition, an object of the present invention is to provide an electric wheelchair driving control system capable of driving in a straight direction even when a joystick is operated in a state in which a user's center of gravity is shifted to the left or right side of the wheelchair.

In addition, an object of the present invention is to provide an electric wheelchair driving control system capable of improving safety by removing discontinuous patterns that appear when accelerating, decelerating, or turning the electric wheelchair.

In addition, an object of the present invention is to provide an electric wheelchair driving control system that improves the user's convenience by enabling easy operation only by manipulating a joystick.

In order to achieve the above object, the electric wheelchair driving control system of the present invention that improves the straight driving performance of the present invention generates a driving or rotation signal of an electric wheelchair accelerated or decelerated through a low pass filter (LPF) after receiving an operation signal of a joystick. A motor that controls the driving of the motor by using a signal from the control signal generation unit by having a control signal generation unit, a dynamic model setting unit to which a disturbance object (DOB) is applied, and a speed controller based on YMO (Yaw Moment Observer). Including a control unit, the driving is controlled by the straight direction dynamic model and the rotation direction dynamic role model set in the dynamic model setting unit, and a parameter set in the speed controller.

In addition, in the electric wheelchair travel control system of the present embodiment, the joystick includes four Hall sensors (A, B, C, D), and a pair of Hall sensors (A) in the front and rear directions based on a reference voltage. A low voltage and a high voltage are respectively set between ,C), a low voltage and a high voltage are respectively set between a pair of Hall sensors B and D in the left and rear direction, and the control signal generator includes a pair of Hall sensors A and Depending on whether the voltage applied between C or B and D) is a low voltage or a high voltage with respect to the reference voltage, signals of forward, backward, left turn, and right turn may be generated.

In addition, in the electric wheelchair travel control system of this embodiment, the dynamics model setting unit,

The DOB of is applied (where a is the disturbance, P is the actual system, Q _i and Q _FF are the cutoff frequencies of YMO and feed-forward), and the linear dynamic model is P _long (s) = 1/(24s) +15), and the rotation direction dynamics model may be modeled as P _rot (s) = 1/(29.6s+21.4).

In addition, in the electric wheelchair travel control system of this embodiment, the speed controller,

DOB of is applied, and Kp=0.25, Ki=0.0035, J _n =0.006, B _n =0.003, Q _i =15Hz, Q _FF =3Hz can be set (where J _n and B _n are the nominal of the system Model, Q _i and Q _FF are cutoff frequencies of YMO and Feed-forward).

The present invention applies DOB as a dynamics model for controlling the driving of a motor, and by deriving and setting a linear dynamics model and a rotational dynamics model optimized for electric wheelchairs, stable driving can be achieved by minimizing disturbances when going straight and rotating. have.

In addition, in the present invention, a driving signal is generated by first filtering an operation signal transmitted from a joystick, thereby exhibiting stable driving performance for acceleration/deceleration.

In addition, according to the present invention, direction change and acceleration/deceleration are possible only by operation of a joystick, thereby improving user convenience.

1 is a perspective view showing an electric wheelchair according to the present embodiment,
2 is a block diagram showing the main configuration of the electric wheelchair travel control system of the present embodiment;
3 is a conceptual diagram showing the output range of the joystick of the present embodiment;
4 is a block diagram showing a DOB system for deriving a dynamic model of the electric wheelchair driving control system according to the present embodiment;
5 is a block diagram showing a signal transmission process of the electric wheelchair driving control system according to the present embodiment;
6 is a graph showing signal waveforms of a joystick and a motor unit, which are main parts of FIG. 5;
7 is a block diagram showing a DOB system for implementing a YMO-based speed controller of the electric wheelchair driving control system according to the present embodiment;
8 is a diagram showing an experiment for evaluating straight-line driving performance according to the present embodiment;
9 is a view showing the result of the straight driving performance of the electric wheelchair according to the present embodiment and the prior art.

The present invention and the technical problem achieved by the implementation of the present invention will be clarified by the preferred embodiments described below. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

It should be understood that the differences between the present embodiments, which will be described later, are not mutually exclusive. That is, without departing from the spirit and scope of the present invention, specific shapes, structures, and characteristics described may be implemented in other embodiments in relation to one embodiment, and the location of individual components within each disclosed embodiment. Alternatively, it should be understood that the arrangement may be changed, and similar reference numerals in the drawings refer to the same or similar functions over various aspects, and the length, area, thickness, and the like may be exaggerated and expressed for convenience. In the description of the present embodiment, expressions such as up, down, before, after, etc. represent positions or directions relative to each other, and the technical significance thereof is not limited to the dictionary meaning.

1 is a perspective view showing an electric wheelchair according to the present embodiment, FIG. 2 is a block diagram showing the main configuration of the electric wheelchair travel control system of the present embodiment, and FIG. 3 is a conceptual diagram showing the output range of the joystick of the present embodiment.

First, referring to FIG. 1, the electric wheelchair 10 of this embodiment includes a chair 11 on which a user can sit, a backrest 12 installed at the rear of the chair, armrests 13 installed on the left and right upper portions of the chair, It includes a travel control assembly 15 provided under the chair, an electric wheel 16 installed at the rear of the lower chair, and a steering wheel 17 installed at the front of the lower chair, and one armrest 13 has a user operation. A stick 14 is provided for it.

The electric wheelchair 10 having the above configuration controls the forward and backward travel and the left and right direction change by manipulating the direction and the inclination of the stick 14 while the user is seated, and the operation signal generated from the stick 14 is a driving control assembly. It is conveyed to (15). In addition, the driving control assembly 15 controls the driving of the electric wheel 16 according to a signal transmitted from the stick 14 so that the electric wheelchair 10 travels according to the intention of the user. Accordingly, in the electric wheelchair 10 of the present embodiment, the driving control assembly 15 controls the driving according to the signal transmitted from the stick 14. Hereinafter, the traveling control system of the electric wheelchair 10 made in the traveling control assembly 15 will be described in detail.

Referring to FIG. 2, the electric wheelchair driving control system 100 of the present embodiment includes an operation unit 110 for user manipulation and a control signal generation unit 120 that generates a control signal using signals input from the operation unit 110. ), a motor control unit 130 for controlling driving of a motor according to a control signal, and a driving unit 140 for driving an electric wheelchair according to a signal from the motor control unit 130.

Specifically, the operation unit 110 is a configuration for a user to manipulate an electric wheelchair, and is composed of only the joystick 111 and the power button 112, and is provided on the handle of one side. That is, the operation unit of the present embodiment is configured to enable acceleration, deceleration, and direction change operation through the joystick 111, and the touch or switching type button is composed of only the power button 112 that supplies power to the electric wheelchair.

The joystick 111 may have a conventional stick structure, and includes four Hall sensors (A, B, C, D) arranged in front, rear, left, and right sides with respect to the center as shown in FIG. 3. The joystick 111 generates a signal such as traveling in the front and rear directions or turning in the left and right directions according to the voltage applied to the Hall sensors A, B, C, and D at each position. As an example, the joystick 111 of the present embodiment has a reference voltage set to 2.5v, a voltage of 0.8v to 4.2v is applied to the Hall sensors A and C in the front and rear directions, respectively, and the Hall sensors B in the left and right directions are applied. A voltage of 0.8v to 4.2v is applied to ,D). As described above, the operation unit 110 according to the present embodiment can simultaneously perform driving, turning, and acceleration/deceleration only by manipulating the joystick 111, so that the convenience of user operation can be improved.

The control signal generation unit 120 generates a signal for driving the electric wheelchair by receiving the operation signal of the joystick 111. The control signal generator 120 generates and controls a driving signal and a turning signal, and generates an acceleration and deceleration algorithm. In addition, the control signal generation unit 120 generates an electrical interface signal between the joystick 111 and the driving unit 140 and sets control parameters.

When the user manipulates the joystick 111, the control signal generation unit 120 displays Table 1 according to the voltage detected between the front and rear Hall sensors A and C and the left and right Hall sensors B and D. It generates the same control signal.

Hall sensor Forward Backward Left Right A Low(0.8v) High(4.2v) - - B - - Low(0.8v) High(4.2v) C Low(0.8v) High(4.2v) - - D - - Low(0.8v) High(4.2v)

Referring to Table 1, the control signal generator 120 generates a forward driving signal when a low voltage (0.8v) lower than the reference voltage (2.5v) is received between the Hall sensors A and C in the front and rear directions, When a high voltage (4.2v) higher than the reference voltage is received, it generates a reverse driving signal. In addition, the control signal generation unit 120 generates a rotation signal in the left direction when a low voltage (0.8v) lower than the reference voltage is received between the hall sensors B and D in the left and right directions, and a high voltage higher than the reference voltage ( When 4.2v) is received, it generates a right-hand turn signal. At this time, a signal for accelerating or decelerating speed or rotation is generated according to a difference from the reference voltage (2.5v).

In addition, the control signal generation unit 120 includes an LPF to control acceleration/deceleration by filtering a signal from the operation unit 110.

The motor control unit 130 controls driving of the BLDC motor by using the signal generated by the control signal generation unit 1210. The motor control unit 130 includes circuits such as an inverter, a dynamics model setting unit, a current (speed) controller, and an overcurrent blocking circuit. The current controller can be implemented as a PI controller and controls the driving speed of the motor by adjusting three parameters: Kp, Ki, and Ka. In addition, the motor control unit 130 further includes various types of sensors, and includes an acceleration sensor and a gyro sensor along with a hall sensor.

The acceleration sensor and the gyro sensor measure the motion of the electric wheelchair, and provide values of the current straight speed and rotational angular velocity of the electric wheelchair in order to derive the driving control algorithm of the electric wheelchair. The acceleration sensor is used in combination with the Hall sensor to derive the speed in the straight direction, and the gyro sensor is used to derive the angular velocity in the rotation direction of the electric wheelchair. That is, the information detected by the acceleration sensor and the gyro sensor is used as information to improve the stability of driving and riding comfort of an electric wheelchair, and is used to derive a straight forward dynamic model and a rotation direction dynamic model of an electric wheelchair. The motor control unit 130 drives the driving unit 140 based on the derived linear direction dynamics model and the rotational direction dynamics model.

The driving unit 140 drives the electric wheel by generating rotational power under the control of the motor controller 130, or brakes the electric wheel by blocking the rotational power. For this, the driving unit 140 may include a motor unit 141 and a wheel unit 142, and the motor unit 141 is composed of a BLDC motor.

The power supply unit 150 is configured to supply power to the control signal generation unit 120 and the motor control unit 130, and supply power to the control signal generation unit 120 and the motor control unit 130, respectively, with the operation unit 110 and It is transmitted to the driving unit 120.

Hereinafter, a dynamic model constituting the electric wheelchair driving control system of the present embodiment and driving characteristics according thereto will be described. 4 is a diagram showing a DOB system for deriving a dynamic model of the electric wheelchair driving control system according to the present embodiment, and FIG. 5 is a diagram showing a signal transmission process of the electric wheelchair driving control system according to the present embodiment, and FIG. 6 Is a graph showing the signal waveforms of the joystick and the motor unit, which are the main parts of FIG. 5, and FIG. 7 is a diagram showing a DOB system for implementing a YMO-based speed controller of the electric wheelchair driving control system according to the present embodiment, and FIG. It is a diagram showing a straight driving performance evaluation experiment according to an embodiment, and FIG. 9 is a view showing a straight driving performance result of the electric wheelchair according to the present embodiment and the prior art.

One. Derivation of a co-role model

The straight driving of the electric wheelchair is implemented by applying a controller that compensates for disturbances in the rotational direction that obstruct the straight driving. In this embodiment, in order to compensate for the disturbance (a), the dynamics model-based Disturbance OBserver (DOB) was applied as shown in FIG. 4, and the dynamics model (P _n (s)) of the electric wheelchair was derived through an experimental method. Here, Joy _rot is a joystick rotation direction input signal, and Q _FF P _n is a feed forward controller. In addition, a represents the disturbance, P represents the actual system, and Q _i and Q _FF represent the cutoff frequencies of YMO and feed-forward.

The motion of the electric wheelchair is divided into straight, turning, and rotary motions according to the driving direction, but since the turning motion can be expressed as a linear combination of linear and rotary motion, a dynamic model for the longitudinal and rotary direction. Only is derived by the following equation. In addition, the experimental method used to derive the dynamics model of the electric wheelchair is the ratio of the signals input to the system at various frequencies of the same size and the signals output at this time in a Bode graph, so that the predicted value is expressed in the actual measured value. It is obtained by comparing and adjusting.

1) Straight-direction co-role model

In the dynamics model applied in the DOB system, the linear dynamics model is defined as the following equation.

(여기서, M은 전동 휠체어의 공차 중량이고, D는 댐핑 값이다)

(Where M is the tolerance weight of the electric wheelchair and D is the damping value)

In order to implement the driving in the straight direction of the electric wheelchair, the electric wheel of the rear wheel must be rotated in the same direction from the input signal, and the steering wheel (caster) of the front wheel must be fixed in the straight direction. The input signal is selected in the form of a Sin function due to the system characteristics of the electric wheelchair, and is set in the low frequency range of 1Hz ~ 0.05Hz in consideration of the weight.

The weight (M) of the model predicted according to the result measured at the tolerance weight of the electric wheelchair is about 24 kg, and the damping (D) is adjusted to a value similar to the experimental result in consideration of the fact that it is difficult to measure in practice. As a result, the dynamic model in the straight direction of the electric wheelchair is set as P _long (s)=1/(24s+15).

2) Rotation direction dynamic model

In the dynamics model applied in the DOB system, the rotational direction dynamics model is defined as the following equation.

(여기서, J는 회전방향 2차 관성모멘트이고, B는 회전방향 마찰이다.)

(Here, J is the second moment of inertia in the rotational direction, and B is the friction in the rotational direction.)

In order to implement the rotation direction of the electric wheelchair, the electric wheels of the rear wheels must be rotated in opposite directions with the same size from the input signal, and the steering wheels (casters) of the front wheels are allowed to move freely without being fixed in a specific direction.

The dynamic model value used when configuring the DOB for the rotation direction controls the disturbance in the rotation direction and acts as a parameter that affects the performance of the controller. The rotational direction dynamic model of this embodiment was derived by the general frequency response method used to derive the system characteristics, and as a result, the rotational direction dynamics model of the electric wheelchair is P _rot (s) = 1/(29.6s+21.4 ).

2. Implementation of driving stability technology

In this embodiment, an acceleration/deceleration profile and a YMO-based speed controller are used to implement driving stability.

1) Implementation of technology to improve ride comfort using acceleration/deceleration profile

Since the driving speed of the electric wheelchair is adjusted from the input signal of the joystick, sudden acceleration or rapid deceleration is determined according to the user's operation state. Since the joystick lever has a narrow operating range and it is difficult for the user to finely adjust the operation while driving, in this embodiment, the value input from the joystick as shown in FIG. 5 is a control signal through the primary LPF (Low Pass Filter). Pass it to the generator. The speed generated when operating the joystick lever implements the speed input value as a speed input value to which acceleration/deceleration is applied through the proposed primary LPF, and at this time, the control signal generation unit detects the forward and backward direction when operating the lever together with the LPF processing unit. It can have wealth.

In the electric wheelchair to which the acceleration/deceleration profile is applied as in this embodiment, the motor drive B is capable of smooth acceleration/deceleration in response to the sudden joystick input signal A as shown in FIG. 6.

2) YMO-based speed controller implementation

FIG. 7 is a block diagram of a controller using a YMO (Yaw Moment Observer) for straight driving of an electric wheelchair, and an input speed value represents the speed in the rotational direction of the electric wheelchair when driving straight, so it is maintained at zero. Here, Joy _rot is a joystick rotation direction input signal, C is a feedback controller, and Q _FF P _n is a feed forward controller.

In this embodiment, a feed forward and a feedback controller are configured together in the YMO in order to remove disturbances that obstruct the driving in the straight direction.

When the driving direction of the electric wheelchair is changed (forward <-> backward), the direction of the steering wheel (caster) is changed, thereby generating a disturbance at a specific point in the electric wheelchair, but according to this embodiment, the disturbance is removed from the YMO-based controller. do. Therefore, even if the disturbance caused by the caster acts on the electric wheelchair according to the change of the driving direction, the straight driving can be stably maintained.

3. Straight running performance test

The straight driving performance of the electric wheelchair according to the present embodiment is expressed as a quantitative value by measuring the distance the electric wheelchair is separated from the center line in the straight direction after driving a distance of 10 m and dividing it by the driving distance. As a result of the experiment, it was confirmed that the performance for driving in the straight direction has an average error of 0.9% (9cm). The error for the straight-line driving performance is determined according to the parameter setting value of the proposed controller, and in this experiment, as shown in Fig. 8, Kp=0.25, Ki=0.0035 in the PI controller is set, and J _{n in the YMO speed controller} When set to =0.006, B _n =0.003, Q _i =15Hz, and Q _FF =3Hz, the most ideal straight driving was shown. Here, J _n and B _n are the nominal models of the system, respectively, and Q _i and Q _FF are the cutoff frequencies of YMO and Feed-forward, respectively.

On the other hand, looking at the results of the straight driving performance of the electric wheelchair according to the present embodiment and the prior art, as shown in Fig. 9, in particular, when proceeding in a straight direction on a surface with a fine inclination, a conventional electric wheelchair has a lower side of the slope. Although the moving direction moves in the direction, the electric wheelchair according to the present embodiment is stably driven in the straight direction with little change in position. At this time, the distance (L:X~X') away from the central axis of the conventional electric wheelchair appears remarkably as the moving distance or inclination from the starting point increases, but the electric wheelchair of this embodiment is centered almost irrespective of the moving distance or inclination from the starting point. Proceed while holding the axis.

As described above, exemplary embodiments of the present invention have been shown and described, but various modifications and other embodiments may be made by those skilled in the art. These modifications and other embodiments are all considered and included in the appended claims and will not depart from the true spirit and scope of the present invention.

10: electric wheelchair
100: electric wheelchair driving control system
110: control panel
120: control signal generator
130: motor control unit
140: drive unit

Claims (4)

A control signal generator configured to generate a driving or rotation signal of an electric wheelchair accelerated or decelerated through a low pass filter (LPF) after receiving an operation signal of the joystick; And,
Including; a motor control unit including a dynamic model setting unit to which a disturbance OBserver (DOB) is applied and a speed controller based on a yaw moment observer (YMO) and controlling driving of the motor using a signal of the control signal generation unit;
A driving control system for an electric wheelchair that improves linear driving performance, in which driving is controlled according to a driving direction dynamic model and a rotation direction dynamic role model set in the dynamic model setting unit, and a parameter set in the speed controller. The method of claim 1,
The joystick includes four Hall sensors (A, B, C, D), and a low voltage and a high voltage are respectively set between a pair of Hall sensors (A, C) in the front and rear directions based on a reference voltage, Low voltage and high voltage are set between the pair of Hall sensors (B,D) in the left and rear direction, respectively,
The control signal generator generates signals of forward, backward, left turn, and right turn according to whether the voltage applied between the pair of Hall sensors (A, C or B, D) is a low voltage or a high voltage with respect to the reference voltage, Electric wheelchair driving control system with improved straightness driving. The method of claim 2,
The dynamics model setting unit,

The DOB of is applied (where a is the disturbance, P is the actual system, Q _i and Q _FF are the cutoff frequencies of YMO and feed-forward),
The straight forward dynamics model is modeled as P _long (s) = 1/(24s+15),
The rotational direction dynamics model is modeled as P _rot (s)=1/(29.6s+21.4), an electric wheelchair driving control system with improved straightness driving. The method of claim 3, wherein the speed controller,

The DOB of is applied, and Kp=0.25, Ki=0.0035, J _n =0.006, B _n =0.003, Q _i =15Hz, Q _FF =3Hz. J _n and B _n are the nominal models of the system, Q _i and Q _FF are the cutoff frequencies of YMO and feed-forward).

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