Control of an electric wheelchair using an inertial measurement system or an acceleration sensor

Abstract

Device (100) for controlling an electrically powered wheelchair (140), the device comprising: an inertial measuring device (110) with an acceleration sensor (111) which is designed to record a movement of the inertial measuring device (110), wherein the inertial measuring device (110) is designed to determine its position and in particular changes in this position in two- or three-dimensional space, and to generate a movement signal based thereon using a filter algorithm; a control device (120) which is designed to receive the movement signal, to calculate a direction of travel and a speed of the wheelchair (140) based on the movement signal and to generate a control signal based thereon; and a drive device (130) which is designed to receive the control signal and to separately control at least one of two mutually independent main wheels of the wheelchair (140) in accordance with the control signal, wherein the inertial measuring device (110) is designed to measure a movement structure of a user of the wheelchair (140) with a calibration and to adapt the movement signal thereto in accordance with the movement structure, and wherein a movement direction of the inertial measuring device (110) is determined by the user with the calibration.

Description

[0001] The invention relates to a method and a device for controlling an electric wheelchair by means of an inertial measuring system.

[0002] When controlling an electrically powered wheelchair or other self-propelled electric mobility devices, there are various options for the device that processes user inputs. On the one hand, joysticks are used: small levers that are deflected from a central rest position. The speed of the wheelchair is determined by the degree to which the joystick is deflected forwards or backwards, and the direction of travel of the wheelchair is determined by the degree to which the joystick is deflected to the sides. On the other hand, touchpads or touchscreens can be used: touch-sensitive surfaces where the control signals result from a position of the user input on the touch-sensitive surface. Starting from a central position on the touchpad, the speed of the wheelchair is calculated from the distance forwards or backwards from a position of a user input on the touchpad to the central position.The wheelchair's direction of travel can be calculated from the lateral distance or angle of the position of the user input on the touchpad to an imaginary centerline. The wheelchair can be stopped by ending the user input on the control interface, for example, when the user lifts their finger from the touchpad. Systems that use inertial measurement units to control the wheelchair are also in use. However, all of these control devices require the user to meet certain requirements to operate the device. Not every user, with their individual needs and specific motor skills and limitations, is able to comfortably control one of the existing control systems.

[0003] From US 2017 / 0 259 811 A1, an electrically powered mobility device is known which offers the user the possibility to move safely in expected environments of daily life, including the ability to maneuver in confined spaces and overcome curbs, stairs and other obstacles, as well as to travel safely and comfortably in vehicles.

[0004] It is therefore an object of the invention to provide an improved control for electrically operated wheelchairs.

[0005] The object is achieved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims, the following description, and the figures.

[0006] According to a first aspect of the invention, a device for controlling an electrically powered wheelchair is provided, the device comprising: an inertial measuring device with an acceleration sensor, which is designed to record a movement of the inertial measuring device, wherein the inertial measuring device is designed to determine its position and in particular changes in this position in two- or three-dimensional space and to generate a movement signal based thereon using a filter algorithm, a control device, which is designed to receive the movement signal, calculate a direction of travel and a speed of the wheelchair based on the movement signal and generate a control signal based thereon, and a drive device, which is designed toto receive the control signal and to separately control at least one of two independent main wheels of the wheelchair according to the control signal. The inertial measuring device is designed to measure a movement pattern of a wheelchair user using a calibration and to adapt the movement signal accordingly. The direction of movement of the inertial measuring device is determined by the user using the calibration.

[0007] An inertial measuring device is used in a device according to the invention for controlling an electrically powered wheelchair. An inertial measuring device is any device capable of determining the position of the device, and in particular changes in the position of the device, in two- or three-dimensional space using one or more acceleration and / or yaw rate sensors. These devices, also known as IMUs (inertial measurement units), can also be specifically designed for this purpose, or they can be equipped with corresponding sensors in addition to their main functions. For example, smartphones, smartwatches, or navigation devices can often be used as inertial measuring devices. The inertial measuring device can also be spatially separated from the control device or drive device and communicatively coupled via a cable, Wi-Fi, or near-field connection.To control the wheelchair, a wheelchair user performs a movement using the inertial measuring device. This movement is recorded by the inertial measuring device, and a movement signal corresponding to the movement is generated. A filter algorithm is used for this purpose, which is advantageously adapted to the respective wheelchair user. The movement signal is used to calculate the desired direction of travel and speed of the wheelchair and to generate a control signal. The control signal, in turn, is used to control the main wheels of the wheelchair independently of one another in order to achieve the desired direction of travel and speed. It is assumed that the wheelchair has a driven wheel on both the left and right. Cornering is achieved by rotating the wheels on each side at different speeds.It is also possible for one wheel to be stationary while the opposite wheel rotates, as well as for the two driven wheels to rotate in opposite directions. However, it should be understood that wheelchairs, and generally any type of electrically powered vehicle, can also be controlled using the device according to the invention, regardless of how the driven and / or steered wheels are arranged.

[0008] According to the invention, the inertial measuring device is designed to measure a movement structure of a user of the wheelchair with a calibration and to adapt the movement signal to the movement structure.

[0009] To control the wheelchair, the inertial measuring device is calibrated by a wheelchair user in this embodiment of the invention. This can be done for the first time when the inertial measuring device is put into operation or several times at the user's request. In the process, the control system and, in particular, the filter algorithm are adapted to the needs of the wheelchair user. In the context of the device according to the invention, the movement structure means, among other things and primarily, that the sensitivity of the movement recording is adapted to the user's motor abilities. Depending on the user's requirements, either a low-amplitude movement by the user may be sufficient to control the wheelchair, or the user's movement for controlling the wheelchair may be overlaid by unwanted movements.In this case, the filter algorithm recognizes the unwanted movements as such and filters them out of the motion signal.

[0010] In one embodiment of the invention, the inertial measuring device is designed to be attached to a body part of the user.

[0011] In this embodiment of the invention, the inertial measuring device can be attached to any part of the user's body. It is not necessary to hold it in one hand, for example, if the user's hands are needed for other activities or are not available for control for other reasons. This allows the inertial measuring device to be moved with the head, for example, by nodding or rotating. Likewise, the inertial measuring device can be attached to the user's arms or legs, or even, for example, to a single finger. This makes it possible to accommodate the user's individual requirements and movement limitations.

[0012] According to the invention, a direction of movement of the inertial measuring device is determined by the user with the calibration.

[0013] In addition to the user's individual movement structure, the adaptation of the inertial measuring device also extends to the assignment of the inertial measuring device's movement axes to the respective functions of the wheelchair. In this embodiment of the invention, calibration determines the axes used for control. Two independent axes are advantageous, with a first axis used to control the wheelchair's direction of travel and a second axis used to control the wheelchair's speed. In this context, "axis" or "direction of movement" refers to a direction of translation or a direction of rotation, although combinations of translation and rotation are also conceivable.In principle, the axes can be freely selected by the user, but it is advantageous if independent directions of movement are defined for controlling the direction of travel and for controlling the speed.

[0014] In one embodiment of the invention, a zero position and / or a maximum position of the movement of the inertial measuring device is determined by the user with the calibration.

[0015] During calibration, the user determines the spatial position in which the inertial measuring device is in a neutral position, i.e., the position in which no movement of the wheelchair occurs. This embodiment of the invention also determines the permissible movement of the inertial measuring device, i.e., the amplitude of the inertial measuring device's movement that triggers the wheels to operate at, for example, maximum speed or minimum turning radius. This allows for optimal adaptation of the wheelchair's driving characteristics to the user.

[0016] In one embodiment of the invention, the drive device is designed to continuously control at least one of two independent main wheels of the wheelchair in accordance with the control signal.

[0017] Continuous control of the wheelchair should be understood to mean that the speed of the wheelchair is related to the deflection of the inertial measuring device from the zero position at that time. In this embodiment, the speed of the wheelchair can, for example, be proportional to the deflection of the inertial measuring device from the zero position. Increasing the deflection leads to acceleration, while moving the inertial measuring device back to the zero position leads to the wheelchair braking to a standstill. The same applies to the direction of travel. In this case, the steering angle is related, for example, to the deflection of the inertial measuring device from the zero position. The steering angle follows the corresponding deflection from the zero position in which the inertial measuring device is currently located. The steering angle should be understood as a measure of the curve radius of a corner being driven.The larger the steering angle, the smaller the turning radius. The steering angle can be determined, for example, by the ratio of the rotational speeds of the wheelchair's two main wheels, or the wheelchair can be steered by wheels that rotate around a vertical axis.

[0018] In one embodiment of the invention, the drive device is designed to use pre-stored movement sequences of the inertial measuring device to control additional functions of the wheelchair.

[0019] With a device according to the invention, it is also possible to control other functions of the wheelchair in addition to the direction of travel and speed. For this purpose, for example, movements of the inertial measuring device relative to a third spatial direction can be used. It is also possible to perform specific sequences of movements of the inertial measuring device in space and compare them with previously stored movement sequences. If the movement sequences match, an additional function of the wheelchair is executed in this embodiment of the invention.

[0020] In one embodiment of the invention, the drive device is designed to use as the additional functions a turning on the spot, an adjustment of a seat of the wheelchair, a switching on of a driving light of the wheelchair or an actuation of a horn of the wheelchair.

[0021] Additional functions are considered to be functions that go beyond controlling the driving functions. In particular, this refers to functions for adjusting the seat position or lighting.

[0022] A further aspect of the invention comprises a wheelchair with a device according to one of the embodiments described above, wherein the drive device is designed to control at least one of two mutually independent main wheels separately.

[0023] In the context of the present invention, however, any vehicle that is self-propelled and controlled by a user via a device that processes movements of an inertial measuring device in space can also be considered a wheelchair.

[0024] The steering and drive are not necessarily limited to the separate control of two main wheels; any configuration of steered and unsteered wheels can also be controlled with a device according to the invention.

[0025] A further aspect of the invention comprises a method for controlling an electrically powered wheelchair, the method comprising the following steps: A first step comprises adapting a filter algorithm to a movement structure of a user of the wheelchair using a calibration. A second step comprises recording a movement of an inertial measuring device. A third step comprises generating a movement signal based on the movement using the filter algorithm. A fourth step comprises calculating a direction of travel and a speed of the wheelchair based on the movement signal and generating a control signal. And a fifth step comprises separately controlling at least one of two mutually independent main wheels of the wheelchair according to the calculated direction of travel and speed.

[0026] The wheelchair is controlled according to a process that can be divided into steps. In the first step, the filter algorithm is calibrated to adapt it to the movement structure of the wheelchair user. This means that the axes along which the movements of an inertial measuring device for controlling the wheelchair should occur are determined, and the range along these axes within which control takes place. The filter algorithm also adapts to the user's individual movement pattern, which results from their motor skills. This adaptation allows a reliable distinction to be made between movements intended by the user as control commands and movements that were unintentional or accidental. In the second step, a movement of the inertial measuring device is recorded.The values ​​from the acceleration and angular rate sensors are read in the inertial measurement device. In the third step, a motion signal is generated from the recorded movement using the filter algorithm. Only those portions of the recorded movement that the filter algorithm identifies as intended by the user are reproduced in the motion signal. In the fourth step, the intended direction and speed are calculated based on the motion signal, and a corresponding control signal is generated. In the fifth step, the driven main wheels of the wheelchair are controlled such that their respective rotational speeds cause the wheelchair to move in the corresponding direction and speed.

[0027] Further embodiments of the invention are explained below with reference to the following drawings: Fig. 1 shows a schematic structure of the device according to the invention for controlling a wheelchair. Fig. 2 shows a block diagram of the method according to the invention for controlling the wheelchair. Detailed description of the characters

[0028] Fig. 1 shows a schematic structure of a device 100 according to the invention for controlling a wheelchair 140. The device 100 comprises an inertial measuring device 110 with an acceleration sensor 111, a control device 120, and a drive device 130. The inertial measuring device 110 uses the acceleration sensor 111 to record a movement of the inertial measuring device 110 and generates a movement signal based thereon using a filter algorithm. The control device 120 receives the movement signal, calculates a direction of travel and a speed of the wheelchair 140 based on the movement signal, and generates a control signal based thereon. The drive device 130 receives the control signal and, in accordance with the calculated direction of travel and speed, separately controls at least one of two mutually independent main wheels of the wheelchair 140 in accordance with the control signal.

[0029] Fig.2 shows a block diagram of the method according to the invention for controlling a wheelchair 140. A first step S1 of adapting a filter algorithm to a movement structure of a user of the wheelchair 140 with a calibration is followed by a second step S2 of recording a movement of an inertial measuring device 110. In a third step S3, a movement signal based on the movement is generated using the filter algorithm. In a fourth step S4, a direction of travel and a speed of the wheelchair 140 are calculated based on the movement signal, and a control signal is generated. And in a fifth step S5, at least one of two mutually independent main wheels of the wheelchair 140 is separately controlled according to the calculated direction of travel and speed.

Claims

[1] Device (100) for controlling an electrically powered wheelchair (140), the device comprising: an inertial measuring device (110) with an acceleration sensor (111) which is designed to record a movement of the inertial measuring device (110), wherein the inertial measuring device (110) is designed to determine its position and in particular changes in this position in two- or three-dimensional space, and to generate a movement signal based thereon using a filter algorithm; a control device (120) which is designed to receive the movement signal, to calculate a direction of travel and a speed of the wheelchair (140) based on the movement signal and to generate a control signal based thereon; and a drive device (130) which is designed to receive the control signal and to separately control at least one of two mutually independent main wheels of the wheelchair (140) in accordance with the control signal, wherein the inertial measuring device (110) is designed to measure a movement structure of a user of the wheelchair (140) with a calibration and to adapt the movement signal thereto in accordance with the movement structure, and wherein a movement direction of the inertial measuring device (110) is determined by the user with the calibration. [2] Device (100) according to claim 1, wherein the inertial measuring device (110) is designed to be attached to a body part of the user of the wheelchair (140). [3] Device (100) according to one of the preceding claims, wherein a zero position and / or a maximum position of the movement of the inertial measuring device (110) is determined by the user with the calibration. [4] Device (100) according to one of the preceding claims, wherein the drive device (130) is designed to continuously control at least one of two mutually independent main wheels of the wheelchair (140) in accordance with the control signal. [5] Device (100) according to one of the preceding claims, wherein the drive device (130) is designed to use pre-stored movement sequences of the inertial measuring device (110) to control additional functions of the wheelchair (140). [6] Device (100) according to claim 5, wherein the drive device (130) is designed to use as the additional functions a turning on the spot, an adjustment of a seat of the wheelchair (140), a switching on of a headlight of the wheelchair (140) or an actuation of a horn of the wheelchair (140). [7] Wheelchair (140) with a device (100) according to one of the preceding claims, wherein the drive device (130) is designed to control at least one of two mutually independent main wheels separately. [8] A method for controlling an electrically powered wheelchair (140), the method comprising the steps of: - Controlling the electrically powered wheelchair (140) by means of a device (100) according to one of claims 1 to 6, - adapting a filter algorithm to a movement structure of a user of the wheelchair (140) with a calibration (S1), - recording a movement of an inertial measuring device (110) (S2), - Generating a motion-based motion signal using the filter algorithm (S3), - calculating a direction of travel and a speed of the wheelchair (140) based on the movement signal and generating a control signal (S4), and - separately controlling at least one of two independent main wheels of the wheelchair (140) according to the calculated direction of travel and speed (S5).

Images