WO2016110557A1

WO2016110557A1 - Control of motorized wheelchair

Info

Publication number: WO2016110557A1
Application number: PCT/EP2016/050247
Authority: WO
Inventors: Gert SPENDER-ANDERSEN; Søren MØRCH
Original assignee: Tks A/S
Priority date: 2015-01-08
Filing date: 2016-01-08
Publication date: 2016-07-14
Also published as: EP3242646A1

Abstract

The invention relates to a control system for a motorized wheelchair, said control system comprising: a touch sensor providing a touch-sensitive area for sensing input through a body limb making contact with the touch- sensitive area; and a processing unit, which is arranged to receive an input signal from the touch sensor, wherein the processing unit is further arranged to convert the input signal to speed and direction information based on an input position on the touch-sensitive area and to transmit a control signal comprising the speed and direction information for controlling driving of the motorized wheelchair; wherein the processing unit is further arranged to receive a stop signal in response to a body limb releasing contact with the touch-sensitive area or a plurality of body limbs making contact with the touch-sensitive area.

Description

CONTROL OF MOTORIZED WHEELCHAIR

Technical Field

The present invention relates to a control system for a motorized wheelchair and a method for controlling a motorized wheelchair.

Background of the Invention

Persons with movement disabilities due to spinal cord injuries, brain injuries or other impairments of the motoric system may be greatly affected in everyday life, as their lack of motoric skills may reduce their abilities of interacting with external aids such as computers, telephones, wheelchairs, etc. via standardized user interfaces.

The interaction with external aids may be very important for persons with movement disabilities; as such external aids may assist the persons in living on a self-supportive independent basis and may have a huge impact on their quality of life.

There exists a vast amount of assistive technologies that may be used to improve the quality of life for persons with impairments to the motoric system, such as breath controlled wheelchairs, for persons that have very limited motoric skills, such as tetraplegics that have lost their motoric skills in their torso, legs and arms. However, breath controlled wheelchairs may have a relative small input range, which means that the breath control can only be used in a limited manner, and may only be used to control simple functions.

Summary of the Invention

It is an object of the invention to provide an improved user interface for enabling control of a motorized wheelchair. It is a specific object of the invention to provide a user interface which may be adapted for use by persons having some sensory/motoric signal transmission into their arms.

These and other objects of the invention are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims. According to a first aspect of the invention, there is provided a control system for a motorized wheelchair, said control system comprising: a touch sensor providing a touch-sensitive area for sensing input through a body limb making contact with the touch-sensitive area; and a processing unit, which is arranged to receive an input signal from the touch sensor, said input signal comprising an input position on which contact by the body limb with the touch- sensitive area is detected, wherein the processing unit is further arranged to convert the input signal to speed and direction information based on the input position and to transmit a control signal comprising the speed and direction information for controlling driving of the motorized wheelchair; wherein the processing unit is further arranged to receive a stop signal in response to a body limb releasing contact with the touch-sensitive area or a plurality of body limbs making contact with the touch-sensitive area.

According to a second aspect of the invention, there is provided a method for controlling a motorized wheelchair, said method comprising:

detecting contact of a body limb with a touch-sensitive area of a touch sensor; generating an input signal comprising coordinates of an input position on which contact by a body limb occurred, such that the input signal is

convertible to speed and direction information for controlling driving of the motorized wheelchair; detecting the body limb releasing contact with the touch-sensitive area; and generating a stop signal in response to the detection of the body limb releasing contact or detection of a plurality of body limbs making contact with the touch-sensitive area.

According to a third aspect of the invention, there is provided a computer program product comprising computer code instructions for performing the method according to second aspect when run on an apparatus having processing capability.

Thanks to the invention, there is provided a touch-sensitive area for enabling a user to provide input through a touch interface. The user may thus control the motorized wheelchair by means of a body limb in contact with the touch-sensitive area. This allows a user interface to be provided with more advanced functionalities than possible via e.g. breath control. Thanks to the invention, the motorized wheelchair may be quickly brought to a halt allowing persons with impairments to the motoric system to be able to safely drive the wheelchair. In particular, a stop signal may be generated as soon as a body limb releases contact with the touch-sensitive area or a plurality of body limbs make contact with the touch-sensitive area.

As used herein, the term "body limb" should be construed as any part of an arm or a leg that may be used to control the wheelchair, such as a finger, a toe or an elbow.

According to an embodiment of the first aspect of the invention, the received stop signal comprises an input position corresponding to a neutral point. The motorized wheelchair may be provided with a drive unit receiving input from a control input installed on the wheelchair, such as a joystick for controlling driving of the wheelchair. The control system according to the invention may be connected to the existing drive unit providing input similar to the input provided by the joystick. Hence, a stop signal may be provided as an input position corresponding to the joystick being brought to a neutral point.

According to a further embodiment, the touch sensor is embedded in a touch screen, such as a touch screen of a smart phone, providing a display for presenting information to a user. This implies that a user may receive information relevant to the controlling of the wheelchair on the touch screen. The information presented to the user may be dynamically changed, whereby the user interface allows for advanced interaction with the user.

In one embodiment, the touch screen of a smart phone is used and the smart phone may be provided with an application specially adapted for controlling the motorized wheelchair. A user may typically carry a mobile phone in order to be able to make phone calls, communicate through text messages, etc. By providing the control of the wheelchair through a mobile phone application, the user may be able to make use of the mobile phone also for the driving of the wheelchair. Thus, there is no need for the user to interact with a separate input device for driving the wheelchair.

The touch sensor may provide an input interface for receiving touch input in order to control further functions of the motorized wheelchair, such as adjustment of seat up or down, backrest up or down, complete chair up or down. Hence, the user may be able to control the wheelchair exclusively via the touch sensor providing both control of the driving of the wheelchair and controlling settings of the wheelchair.

According to an embodiment, the processing unit being arranged to convert the input signal to speed and direction information makes use of an algorithm for promoting maintaining of a forward direction of the wheelchair. Hence, the processing unit may help the user in driving the wheelchair in a forward direction, such that constant small adjustments of the direction of the wheelchair may be avoided when the user desires to drive the wheelchair forward.

According to a specific embodiment, a neutral point is defined on the touch-sensitive area, speed information is dependent of a distance from the neutral point and direction information is dependent of the relation of the input position in a coordinate system to the neutral point, wherein said algorithm defines a forward area extending from the neutral point, being centered around an axis corresponding to a straight forward direction and having an increasing width along the axis away from the neutral point, such as the forward area being V-shaped, and wherein the processing unit is arranged to convert the input signal comprising an input position within the forward area to a straight forward direction.

When a user provides input corresponding to an increased speed of the wheelchair, it may be anticipated that the user wants to drive the wheelchair in a straight forward direction. Hence, using an algorithm that defines the forward area having an increasing width along the axis away from the neutral point, it is easier to drive the wheelchair in a straight forward direction when using a high speed of the wheelchair.

According to another embodiment, the processing unit is further arranged to monitor correctness of the input signal and/or monitor

communication between the touch sensor and the processing unit functioning properly, and wherein the processing unit is further arranged, in response to the monitoring detecting an incorrect input signal or the communication not functioning properly, to generate and transmit a safety action signal, wherein the safety action signal causes at least one of reducing speed of the wheelchair, setting a joystick control of the wheelchair into neutral position, and stopping the wheelchair completely.

The processing unit may be arranged to generate a safety action signal in response to detection of at least one of the following conditions: a time elapsed since last received input signal exceeding a threshold, a number of received input signals per time unit being below a threshold, the input signal comprising incorrect information, such as an invalid input position, a round- trip time of receipt of a response from a device comprising the touch sensor to a communication test packet transmitted by the processing unit exceeding a threshold or the response not being received within a predicted round-trip time, and a difference between a time stamp of an input signal and a current time of the processing unit exceeding a threshold.

By monitoring that the input to the driving of the wheelchair works properly, it may be ensured that a safety action is taken before any accident may occur due to errors in the control input.

Brief Description of Drawings

These and other aspects of the present invention will now be described in further detail, with reference to the appended drawings showing

embodiment(s) of the invention.

Fig. 1 is a schematic view of a control system according to an embodiment of the invention.

Fig. 2 is a schematic view of a user interface presented on a screen.

Detailed Description

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person. Referring now to Fig. 1 , a control system for a motorized wheelchair is schematically disclosed. The control system comprises a touch sensor providing a touch-sensitive area for sensing input through a body limb making contact with the touch-sensitive area. The touch sensor may be embedded in a touch screen of a mobile phone, a personal computer (PC) or a tablet PC, as illustrated in Fig. 1. According to an alternative, a touch sensor may be provided as a separate touchpad, specifically adapted to receive touch input.

The touch sensor may operate in one of several ways, including a capacitive sensing and conductance sensing. The most common technology used entails sensing the capacitive virtual ground effect of a finger or a body limb. Capacitance-based touchpad's will however not sense the tip of a pencil or other similar implement. Gloved fingers may also be problematic to sense.

A processing unit may be arranged to receive an input signal from the touch sensor. The processing unit may be arranged in the same physical unit, in which the touch sensor is arranged. For instance, the processing unit may be implemented as a processing unit of a mobile phone, which provides a touch screen for receiving input from a user. The processing unit may thus run an application, which receives the input signal from the touch screen of the mobile phone.

Alternatively, the processing unit may be arranged in a separate device, which receives an input signal from the touch sensor. The separate device may thus be connected via a wire or through wireless communication to the touch sensor. For instance, Bluetooth® communication may provide the input signal from a device in which the touch sensor is embedded, such as a mobile phone, to a control unit, providing the processing unit. The control unit may be mounted on the wheelchair and may be connected through wires to electrical motor(s) for driving the wheelchair. In one embodiment, the control unit may be installed on a wheelchair having existing means for controlling the driving of the wheelchair, such as a joystick. The control unit may thus override, or complement, the input from the existing control means in order to enable control of the wheelchair through a touch interface. Hence, the control system may be installed on existing wheelchairs. The control unit may mimic the input from the existing control means so as to provide appropriate control signals to the electrical motor(s) or to a unit that receives input from the existing control means. Hence, the control unit may e.g. provide control signals corresponding to control by means of a joystick.

As a further alternative, the processing unit may be arranged in several devices, such that the processing may partly occur in a device embedding the touch sensor, such as a mobile phone, and partly occur in another device, e.g. a control unit that may be mounted on the wheelchair.

The input signal to the processing unit may comprise an input position on which contact by the body limb with the touch-sensitive area is detected. The processing unit may be further arranged to convert the input signal to speed and direction information based on the input position and to transmit a control signal comprising the speed and direction information for controlling driving of the motorized wheelchair.

When it is detected by the touch sensor that a body limb is released from contact with the touch-sensitive area or that a plurality of body limbs makes contact with the touch-sensitive area, a stop signal is generated. The processing unit may receive a signal from the touch sensor that a limb has released contact or that a plurality of limbs makes contact. Such a signal may be interpreted as a stop signal. Upon receipt of the stop signal, the

processing unit may be arranged to transmit a control signal to immediately stop the driving of the wheelchair.

In one embodiment, there is provided an application for receiving input from a user through a touch screen interface, as shown in Fig. 2. When a user maneuvers the wheelchair on the touch screen with a finger, toe, hand or any body limb, the wheelchair will move as requested. When a finger, toe, hand or a body limb is removed from the touch screen, the wheelchair goes into stop.

The application may be built in to a smart phone device, a tablet or a computer and works via a touch screen.

The smart phone may be connected wirelessly to a control unit. The control unit is then connected directly to a motorized wheelchair.

The smart phone can be placed in a holder or in a hand when the user is placed in the motorized wheelchair. The touch screen area is defined so that it starts working out of a center area, and the further the body limb is moved from the center area, the higher speed will be provided by the wheelchair. Starting outside the center point will provide a higher starting speed.

The processing unit makes use of an algorithm that will ease the driving forward. This means that if the body limb of the user is sliding a little to the right or left, the wheelchair will continue driving straight forward.

No touch button functions are placed in maneuver area, the drive control is done proportionally from the center point.

The touch screen area can be located and scaled individually on the screen of the tablet or smart phone.

A control system providing a smart phone application for control of motorized wheelchairs may be especially advantageous for severely disabled persons.

Conditions that may be seen as degenerative towards the motoric skills, where the loss of motoric skills may be gradual, due to neural disorders that impair the signal transmission from the brain to the spine, and/or from the spine to the extremities. Such persons may have some sensory/motoric signal transmission into their arms, where the persons may have some control of their hands or their fingers. Such persons may often be assisted in their interaction with external components by arranging a touchpad, mouse, or similar touch based control input where the tips of the fingers may be used to provide control input.

A smart phone application gives the ability to provide an input to a touchpad by the use of a finger or a body limb. A finger or body limb is then capable of registering the position on the smart phone device, and sends it to a control unit wirelessly. The control unit converts the signals to the motorized wheelchair control interface, where they are converted to drive signals. The motorized wheelchair is now driving according to the movement made by a finger or another body limb in the input area on the smart phone or a tablet.

The application allows disabled persons to provide a control input to an motorized wheelchair, via an interface that may be arranged in the finger or other body limb of the user. The structure of the device, in using finger or other body limb of the user ensures that every movement of the smart phone application is registered by the control unit. There are various advantages of using this smart phone application. In existing systems today there are many stand alone systems. The smart phone application on the other hand, allows a user to control the wheelchair in a single unit, where the user can speak on the phone, make a text message, write an email or even just go to the wheelchair application and start driving.

When using the smart phone application, there is a built-in stop function. When using the application, a body limb must always be placed on the touch screen area. As soon as the body limb is lifted, the motorized wheelchair will stop.

It has been observed in testing that a user, when driving forward, makes multiple corrections of the direction. Therefore, the control system makes use of an algorithm that helps the user driving forward. The way the algorithm works is that a forward area is defined as a V-shape. The apex of the V-shape is at the crossing of the axes, i.e. at position 0, 0. The size of the forward driving area then increases proportionally up to the end of the touch- sensitive area for controlling the wheelchair. Inside the V-shaped forward area, the algorithm will correct the imbalance of the finger position into the Y- axis in order to maintain a straight forward direction of the wheelchair.

The smart phone or tablet can take over the existing inputs on the motorized wheelchair, so that the only input for all functions of the wheelchair is provided by the smart phone or tablet. The functions normally placed on a motorized wheelchair is seat up/down, back up/down, complete chair up/down etc. These functions can be built-in to the application.

The control system may further be arranged to provide safety algorithms for trigging a safety action, when a detection of an erroneous condition is made. A safety action may be a reduction in speed, setting the joystick in neutral or stopping the wheelchair completely.

The following safety algorithms may be provided, wherein input device may be the touch sensor or a unit in which the touch sensor is embedded: 1. The control unit monitors the time elapsed since the last received control input from the input device. If the elapsed time is too large the control unit makes a safety action.

2. The control unit counts the number of received (and correct) control inputs per second. If the rate is too low the control unit makes a safety action.

3. The control unit validates the control input from the input device for correctness. If something is deemed wrong (e.g. invalid

coordinates), the control unit rejects the control input and makes a safety action.

4. The control unit monitors the round-trip time (propagation delay) by sending packets with its own clock to the touch sensor. The input device return the value unaltered back. If measured round-trip time (difference between current control unit clock and the received value) is too large, the control unit makes a safety action.

5. The control unit monitors the predicted round-trip time for covering the case when no round-trip time packets are received back. The prediction is made by sending packets at a fixed rate, using the value of the last measured round-trip time and continuously reading the elapsed time since the last received packet. If predicted round- trip time is too large, the control unit makes a safety action.

6. The input device timestamps all control input to the control unit with its own clock. The control unit and input device have at a prior stage synchronized their clocks using a common time

synchronizing algorithm. If the timestamp by the input device is too old when received by the control unit, the control unit rejects the control input and makes a safety action.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Claims

1. A control system for a motorized wheelchair, said control system comprising:

a touch sensor providing a touch-sensitive area for sensing input through a body limb making contact with the touch-sensitive area; and

a processing unit, which is arranged to receive an input signal from the touch sensor, said input signal comprising an input position on which contact by the body limb with the touch-sensitive area is detected, wherein the processing unit is further arranged to convert the input signal to speed and direction information based on the input position and to transmit a control signal comprising the speed and direction information for controlling driving of the motorized wheelchair;

wherein the processing unit is further arranged to receive a stop signal in response to a body limb releasing contact with the touch-sensitive area or a plurality of body limbs making contact with the touch-sensitive area.

2. The control system according to claim 1 , wherein the received stop signal comprises an input position corresponding to a neutral point.

3. The control system according to claim 1 or 2, wherein the touch sensor is embedded in a touch screen, such as a touch screen of a smart phone, providing a display for presenting information to a user.

4. The control system according to claim 3, wherein the touch sensor provides an input interface for receiving touch input in order to control further functions of the motorized wheelchair, such as adjustment of seat up or down, backrest up or down, complete chair up or down.

5. The control system according to any one of the preceding claims, wherein the processing unit being arranged to convert the input signal to speed and direction information makes use of an algorithm for promoting maintaining of a forward direction of the wheelchair.

6. The control system according to claim 5, wherein a neutral point is defined on the touch-sensitive area, speed information is dependent of a distance from the neutral point and direction information is dependent of the relation of the input position in a coordinate system to the neutral point, wherein said algorithm defines a forward area extending from the neutral point, being centered around an axis corresponding to a straight forward direction and having an increasing width along the axis away from the neutral point, such as the forward area being V-shaped, and wherein the processing unit is arranged to convert the input signal comprising an input position within the forward area to a straight forward direction.

7. The control system according to any one of the preceding claims, wherein the processing unit is further arranged to monitor correctness of the input signal and/or monitor communication between the touch sensor and the processing unit functioning properly, and wherein the processing unit is further arranged, in response to the monitoring detecting an incorrect input signal or the communication not functioning properly, to generate and transmit a safety action signal, wherein the safety action signal causes at least one of reducing speed of the wheelchair, setting a joystick control of the wheelchair into neutral position, and stopping the wheelchair completely.

8. The control system according to claim 7, wherein the processing unit being arranged to generate a safety action signal in response to detection of at least one of the following conditions: a time elapsed since last received input signal exceeding a threshold, a number of received input signals per time unit being below a threshold, the input signal comprising incorrect information, such as an invalid input position, a round-trip time of receipt of a response from a device comprising the touch sensor to a communication test packet transmitted by the processing unit exceeding a threshold or the response not being received within a predicted round-trip time, and a difference between a time stamp of an input signal and a current time of the processing unit exceeding a threshold.

9. A method for controlling a motorized wheelchair, said method comprising:

detecting contact of a body limb with a touch-sensitive area of a touch sensor;

generating an input signal comprising coordinates of an input position on which contact by a body limb occurred, such that the input signal is convertible to speed and direction information for controlling driving of the motorized wheelchair;

detecting the body limb releasing contact with the touch-sensitive area; and

generating a stop signal in response to the detection of the body limb releasing contact or detection of a plurality of body limbs making contact with the touch-sensitive area.

10. A computer program product comprising computer code instructions for performing the method according to claims 9 when run on an apparatus having processing capability.