NL2020887B1

NL2020887B1 - Motorized walking aid

Info

Publication number: NL2020887B1
Application number: NL2020887A
Authority: NL
Inventors: Verhoef Wouter
Original assignee: Robot Care Systems B V
Priority date: 2018-05-07
Filing date: 2018-05-07
Publication date: 2019-11-14
Also published as: WO2019216763A1

Abstract

A motorized walking aid comprising a frame and a handle comprises an outer handle structure. An inner handle structure extends in an inner cavity of the outer handle structure and comprising, seen from the frame: a connecting structure, a supporting structure that supports the outer handle structure, a force measurement structure comprising a force sensor, and a coupling structure. The coupling structure comprises a force transfer surface, the outer handle structure comprising a force transfer surface arranged substantially parallel to and facing the force transfer surface of the coupling structure, the outer handle structure being movable in respect of the inner handle structure in a direction normal to the force transfer surfaces. The outer handle structure is configured to transfer via its force transfer surface to the force transfer surface of the coupling structure a force exerted by the user onto the outer handle structure in a direction normal to the force transfer surfaces, wherein the force transfer surface of the outer handle structure is slidable in respect of the force transfer surface of the contact structure.

Description

A61H 3/04 (2018.01) B60L 15/20 (2019.01) B62B 5/00 (2019.01) G01L 1/04 (2019.01) G01L 5/16 (2019.01) (© Afsplitsing van aanvraag , ingediend (30) Voorrang:

^1) Aanvraag ingeschreven: 14 november 2019 (43) Aanvraag gepubliceerd:

Robot Care Systems B.V. te DEN HAAG © Uitvinder(s):

Wouter Verhoef te HAZERSWOUDE-RIJNDIJK © Gemachtigde:

ir. J.C. Volmer c.s. te Rijswijk

47) Octrooi verleend:

november 2019 © Octrooischrift uitgegeven:

november 2019

54) Motorized walking aid

5^ A motorized walking aid comprising a frame and a handle comprises an outer handle structure. An inner handle structure extends in an inner cavity of the outer handle structure and comprising, seen from the frame: a connecting structure, a supporting structure that supports the outer handle structure, a force measurement structure comprising a force sensor, and a coupling structure.

The coupling structure comprises a force transfer surface, the outer handle structure comprising a force transfer surface arranged substantially parallel to and facing the force transfer surface of the coupling structure, the outer handle structure being movable in respect of the inner handle structure in a direction normal to the force transfer surfaces. The outer handle structure is configured to transfer via its force transfer surface to the force transfer surface of the coupling structure a force exerted by the user onto the outer handle structure in a direction normal to the force transfer surfaces, wherein the force transfer surface of the outer handle structure is slidable in respect of the force transfer surface of the contact structure.

NL B1 2020887

Dit octrooi is verleend ongeacht het bijgevoegde resultaat van het onderzoek naar de stand van de techniek en schriftelijke opinie. Het octrooischrift komt overeen met de oorspronkelijk ingediende stukken.

P33473NL00

Motorized walking aid

The invention relates to a motorized walking aid.

A motorized walking aid, such as a motorized rollator, comprises a handle which the user may hold to support himself, such as a handle bar configured to be held by a hand of a user. The motorized walking aid may be driven by an electric motor which is controlled on the basis of a signal provided by a force sensor. The force sensor measures a force applied by the user onto the motorized walking aid. The electric motor is driven, taking an output signal of the force sensor into account.

A person that may use the walking aid, such as an elderly person, a person in a process of physical rehabilitation, a person requiring assistance against dropping down, etc., may make use of the motorized walking aid to support himself resp. herself during walking. Using his/her hands or arms, the user may support himself respectively herself on the walking aid, e.g. on one or two handle bars thereof. In order for the user to manoeuvre the motorized walking aid, various solutions have been devised. As a first possibility, the handle bar(s) may be provided with an input device, such as a switch, a joy stick, etc. Thereby, the user may indicate in what direction, and at what pace, he /she wishes to move the motorized walking aid. As the user may need his/her hands to support himself/herself, another solution has been devised, namely to implement a force sensor in the handlebar(s). The electric motor is driven based on the force as measured. The motorized walking aid may be controlled by the user by pushing the motorized walking aid in the desired direction. Thus, the user may e.g. push the motorized walking aid forward in order for it to drive forward. The electric motor may thereby take account of a majority of the power required to move the motorized walking aid forward. Hence, a user may only require to apply a relatively low force in order to provide that the motorized walking aid moves as desired. The inventors have realized that the forces which the user may exert on the motorized walking aid in order to support himself, thereby placing a substantial weight on the handle, may be orders of magnitude larger than the force which the user may be able to exert in order to direct the motorized walking aid to move. For example, the vertical force by the user supporting himself, may approach a body weight of the user of the walking support. The force applied in forward direction onto the handlebar(s) may need to be very low. As the motorized walking aid, in response to the application of a force onto the handlebars, moves in the direction of the force, the net force the user needs to apply on the handlebars is even lowered due to the assistance of the electrical motor in the same, forward direction. As a result, the inventors have devised that the force applied onto the handlebar in vertical direction may be 500 times or 1000 times larger than the force exerted by the user to direct the motorized walking aid in the desired direction. Nevertheless, an accurate measurement of force, e.g. in a forward direction, may be desired, in order to provide a confidence building user feel and a reliable support to an impaired user.

A problem associated with the motorized walking aid, is that the large vertical force applied by the user onto the handle may result in crosstalk towards the measurement of the horizontal force. Using for example strain gauges, some degree of decoupling may be achieved by using a bridge configuration, for example in that deformation of the strain gauges by the vertical force effects both branches of the bridge, thus, to some extent cancelling each other. However, when using such conventional force measurement techniques in the case of a vertical force which is orders of magnitude larger than the horizontal force, leaning on the handle will result in a cross-coupling between the downwards force and the force measurement of a horizontal force.

It is desired to provide an accurate forward control of the motorized walking aid, even when a person leans on the motorized walking aid, or otherwise exert forces on the walking aid in other directions.

According to an aspect of the invention, there is provided a motorized walking aid comprising a frame, wheels mounted to the frame, at least one motor to drive the wheels, a control unit to control the at least one motor and a handle connected to the frame for enabling a user to hold itself, the handle comprising a force sensor to sense a force exerted by the user on the handle, an output of the force sensor being connected to the control unit, the control unit being configured to control the at least one motor using the force as sensed by the force sensor, the handle comprising:

an outer handle structure comprising a user gripping surface at an outside thereof and defining an inner cavity, and an inner handle structure extending in the inner cavity, the inner handle structure comprising:

o a supporting structure that supports the outer handle structure and having a first end and a second end opposite the first end, o a connecting structure arranged between the first end of the supporting structure and the frame and connecting the supporting structure to the frame, o a force measurement structure comprising the force sensor, the force measurement structure being configured to measure a force between a first end and a second end thereof, the first end of the force measurement structure being connected to the second end of the supporting structure, and o a coupling structure connected to the second end of the force measurement structure, wherein the coupling structure comprises a force transfer surface, the outer handle structure comprising a force transfer surface arranged substantially parallel to and facing the force transfer surface of the coupling structure, the outer handle structure being movable in respect of the inner handle structure in a direction normal to the force transfer surfaces, the outer handle structure being configured to transfer via its force transfer surface to the force transfer surface of the coupling structure a force exerted by the user onto the outer handle structure in a first direction normal to the force transfer surfaces, wherein the force transfer surface of the outer handle structure is slidable in respect of the force transfer surface of the contact structure.

The motorized walking aid may be a rollator, stroller or any other walking aid. The walking aid may comprise a frame that holds wheels, such as 3 or 4 wheels that support the walking aid on the ground. One or more of the wheels are propelled by an electric motor. For example, each wheels is provided with its own motor or 2 of the wheels are provided with a respective motor, or one motor is provided that drives one or more of the wheels by a suitable drive mechanism. At least one handle, e.g. two handles, one per hand, is connected to the frame. The user of the walking aid may support himself respectively herself on the motorized walking aid, thereby holding the handle(s) with his/her hands. Two separate handles may be provided. Alternatively, the handles may be interconnected by an intermediate structure, such as a tube shaped gripping structure. The handle respectively handles comprise a force sensor in order to measure a force applied by the user onto the handle. For example, the handle measures a horizontal force applied by the user in a main direction of movement of the walking aid. A control unit of the walking aid (such as a suitably programmed micro-controller) receives a signal representing the measured force and derives there from a drive signal to drive the at least one electric motor. Hence the user, by exerting a force onto the handle, controls a movement of the motorized walking aid. The user may thereby be required to only apply a fraction of the amount of force that would have been required to push the walking aid forward in case of no motorized support. Further, the motorized walking support may assist the user to propagate forward, as a stable, manageable pace is kept by the walking aid, thus preventing that the user proceeds faster and faster, until the speed has reached a level where the user cannot control him/herself anymore and falls to the ground.

The handle comprises an outer handle structure that forms, at an outside thereof, a gripping surface for the user to hold him/herself. The outer handle structure comprises a cavity, which may extend at least throughout a part of the outer handle structure. The outer handle structure may for example have a generally tubular shape, whereby the cavity extends along a length thereof, e.g. along a axial direction of the tube. An inner handle structure is arranged in the cavity of the outer handle structure. The inner handle structure is connected to the frame. Thus, when the user holds the griping surface of the outer handle structure, forces are transferred from the outer handle structure, directly or via the inner handle structure as explained further below, onto the frame. The outer handle structure is movable, e.g. exhibits some play, in respect of the inner handle structure, e.g. may move in respect of the inner handle structure, e.g. in the direction of movement of the walking support (e.g. in the forward direction). The outer handle structure may be movable in respect of the inner handle structure over a range of micrometres to millimetres. For example, the outer handle structure may be movable over a range of 0.1 millimetre maximum or 0.4 millimetre maximum. The former provides a good user feel with low amount of “play”, while the latter allows more relaxed manufacturing tolerances while still offering a low “play” feel to the user. The inner handle structure successively comprises, seen from the attachment to the frame towards the end of the inner handle structure, a connecting part that connects the inner handle structure to the frame, a support structure that supports the outer handle structure at the inner face thereof, a force measurement structure and a connecting structure. The force measurement structure comprises a force sensor to measure a force between the connecting structure and the support structure.

According to the invention, both the connecting structure and the outer gripper structure comprise a force transfer surface. The force transfer surfaces are vertically oriented and facing each other. The outer handle structure is movable, e.g. exhibits some play, in respect of the inner handle structure in a direction normal to the force transfer surfaces. When the user exerts a force onto the force outer handle structure in the direction normal to the force transfer surfaces, the outer gripper structure pushes against the connecting structure by means of the force transfer surface of the outer handle structure pushing against the force transfer surface of the connecting structure. Thereby, the force in the direction normal to the contacting surfaces (i.e. force transfer surface) in transferred from the outer gripper structure to the connecting structure, hence acting on the measurement structure. As the force sensor of the measurement structure is arranged to measure the force in the direction perpendicular to the normal to the force transfer surfaces, the force applied by the user in the direction normal to the force transfer surfaces may be sensed.

On the other hand, the force transfer surfaces are slidable in respect of each other. Thus, a force applied by the user onto the outer handle structure, in e.g. vertical direction, or in another direction perpendicular to the normal to the force transfer surfaces (e.g. in horizontal direction or a torque about the vertical direction), will to a large extent be decoupled from the force sensor, as on the one hand, a part of this force will divert to the supporting structure which supports the outer handle structure, and on the other hand, a remaining part of the force will result in some movement of the force transfer surface of the outer handle structure in respect of the force transfer surface of the connecting structure. As the force transfer surfaces are slidable in respect of each other, the movement of the outer gripper structure in the direction perpendicular to the normal to the force transfer surface, the movement in respect of the connecting structure, will provide for a sliding of the force transfer surfaces in respect of each other, thus providing a low coupling of the remaining force. The range of movement, in direction perpendicular to the normal, of the outer gripper structure in respect of the supporting structure will typically be small, as the movement may be limited by the supporting structure that fits into the cavity and holds the outer handle structure. As the outer handle structure supports on the supporting structure of the inner handle structure, and as the supporting structure connects to the frame, i.e. guides the vertical or lateral force to the frame thereby bypassing the measurement structure, the force path of the lateral force and vertical force on the handle bypasses the force sensor to a large extend, hence does not, or hardly not affect the force sensor. The measurement structure is bypassed as the supporting structure is supported by the frame via the connecting structure, i.e. bypassing the force sensor.

The handle as described enables to make use of any force sensing using any suitable force sensor. For example, strain gauges may be applied. The measurement structure may hence form a load cell having a measurement direction in the direction normal to the force transfer surface, Due to the vertical force transfer surfaces and the large amount of decoupling, a direct response may be obtained in that the vertical force transfer surfaces will provide for a relatively direct coupling of the force normal to the force transfer surfaces, to the force sensor. Hence, a good user feel may be provided in that, using a force sensor that is relatively stiff in the direction of movement, the forces as applied by the user in the direction normal to the force transfer surface may transfer to the force sensor with a relatively small movement of the outer handle structure in said direction.

In an embodiment, the normal to the force transfer surface extends in a main direction of movement of the motorized walking aid. Hence, a force in the direction of movement of the motorized walking aid, applied by the user onto the handle, may be measured, whereby sideward or vertical forces onto the handlebar may to a large extent be decoupled as explained above.

In an embodiment, the wherein the force transfer surfaces extend in a vertical direction, and wherein the force transfer surface of the outer handle structure is slidable in the vertical direction in respect of the force transfer surface of the contact structure. A force applied by the user onto the outer handle structure in vertical direction will to a large extent be decoupled from the force sensor, as on the one hand, a part of this force will divert to the supporting structure which supports the outer handle structure, and on the other hand, a remaining part of the force will result in some movement in vertical direction of the force transfer surface of the outer handle structure in respect of the force transfer surface of the connecting structure. As the force transfer surfaces are slidable in respect of each other in the vertical direction, the movement of the outer gripper structure in the direction perpendicular to the normal to the force transfer surface, the movement in respect of the connecting structure, will provide for a sliding of the force transfer surfaces in respect of each other, thus providing a low coupling of the remaining force. The range of movement, in direction perpendicular to the normal, of the outer gripper structure in respect of the supporting structure will typically be small, as the movement may be limited by the supporting structure that fits into the cavity and holds the outer handle structure.

In an embodiment, the supporting structure comprises bearings that support the outer handle structure at the inner face thereof, the bearings exhibiting a resiliency in the direction normal to the force transfer surface. Thus, when pushing on the outer handle structure, e.g. in a vertical direction or in any other direction perpendicular to the normal to the force transfer surfaces, the supporting structure supports the outer handle structure. The supporting structure may for example be elongate and extend in the direction of the normal to the force transfer surface. At least two of the bearings may be spaced apart in the direction of the normal to the force transfer surface, so as to enable to accommodate the forces in a direction perpendicular to the normal and support the outer handle structure. The bearings may be connected to the supporting structure, the outer handle structure or both.

When a force is exerted onto the outer handle structure in a direction perpendicular to the normal, the force may provide for an increase of friction between the outer handle structure (i.e. the inner face thereof) and the support structure. As a result of such friction, the force in the direction of the normal to the force transfer surface may be guided, from the outer handle structure, via the frictional interaction between the outer handle structure and the supporting structure, directly to the supporting structure. Hence, no or only a reduced force in the direction of the normal to the force transfer surface would be detected by the force sensor. In order to provide that the outer handle structure remains movable in the direction of the normal to the force transfer surface, the bearings provide a resiliency in the direction of the normal to the force transfer surface. The bearings may for example form leaf springs, thus providing stiffness in the direction perpendicular to the normal (e.g. providing stiffness in the vertical direction) while providing a resiliency in the direction of the normal to the force transfer surface. The stiffness enables to guide the force in the direction perpendicular to the normal (e.g. the vertical force) to the supporting structure, while the resiliency in the direction of the normal to the force transfer surface enables movement of the outer handle structure in respect of the supporting structure in the direction of the normal to the force transfer surfaces, causing the force in the direction of the normal to be guided, at least in part, via the contact structure to the measurement structure comprising the force sensor. Thus, an effect of the friction forces between the outer handle structure and the supporting structure may be avoided. Preferably, the resiliency of the bearings in the direction of the normal is larger than the resiliency of the force measurement structure in the same direction, so that the force acting in the direction of the normal is largely coupled to the force measurement structure, (i.e. the stiffness of the bearings in the direction of the normal is lower than the stiffness of the force measurement structure in the direction of the normal)

In an embodiment, the coupling structure and the outer handle structure comprise mutually facing further force transfer surfaces arranged substantially parallel to the force transfer surfaces, the outer handle structure configured to transfer via the further force transfer surface to the coupling structure a force exerted by the user onto the outer handle structure in a direction normal to the force transfer surface and opposite to the first direction. Thus, further force transfer surfaces may be provided to couple a force in the direction of the normal, opposite to the above mentioned first direction (e.g. a pulling force) to the force measurement structure. Hence, forces in both directions, e.g. pushing and pulling, may be measured. For example, when a user pulls the motorized walking aid to himself / herself, the control unit may drive the electric motor(s) to move the walking aid backwards, i.e. towards the user. Hence, the user may pull the walking aid towards himself/herself with a low force. A range of movement of the outer handle structure In respect of the inner handle structure in the direction of the normal may be limited by the force transfer surface at one end of the range of movement and the further force transfer surface at the other end of the range of movement

In an embodiment, the force sensor comprises two measurement units arranged in a bridged configuration, the two measurement units being arranged, as seen in the vertical direction, symmetrical in respect of a median of the measurement structure, the median extending in the direction of the normal to the force transfer surface. Hence, further decoupling of a force in the direction normal to the force transfer surface may be provided: due to the symmetry in respect of the median, opposite effects on either side may cancel each other. Furthermore, a suitable bridge configuration may be applied to cancel effects on either side of the median. A Wheatstone bridge configuration may be applied, whereby two bridge elements forms measurement units and two bridge elements form reference units as well as provide temperature compensation to compensate for thermal expansion. The measurement units may for example be formed by strain gauges. The bridged configuration may be a half bridge or full bridge configuration.

In an embodiment, in a horizontal direction orthogonal to the normal to the force transfer surface a stiffness of the connecting structure is lower than a stiffness of the supporting structure, a further sensor being arranged at the connecting structure to measure a torque on the supporting structure about a vertical direction. A torque acting on the outer handle structure about the vertical direction may be measured by means of the further sensor. The same applies to a force in the horizontal direction perpendicular to the normal to the force transfer surfaces and exerted onto an end of the handle facing away from the frame, i.e. facing away from the connecting structure. The outer handle structure transfers the torque or force onto the supporting structure that supports the outer handle structure. As one end of the supporting structure is connected to the frame via the connecting structure, the torque or force will act on the connecting structure, which is measured by the further sensor. For example, seen in the vertical direction, one side of the connecting structure is elastically stretched in the direction of the normal to the force transfer surfaces and one side is elastically pressed together in the direction of the normal to the force transfer surfaces. The connecting structure may be somewhat less stiff than the supporting structure by means of a cut out in the material of the connecting structure, e.g. a through hole or a recess. The hole or recess forming a through opening in the vertical direction. An effect of said torque or force on the sensor that measured the force in the direction of the normal to the force transfer surface may be reduced by the decoupling effect of the force transfer surfaces that are able to slide in respect of each other in the direction perpendicular to the normal to the force transfer surfaces.

The further sensor may be arranged at a median of the connecting structure, seen in the vertical direction. Thus, an effect of the vertical force on the connecting structure, may be reduced, as a deformation of the connecting structure due to the vertical force may exhibit a degree of symmetry in respect of the median, hence enabling a degree of cancellation of deformations of the one or more measurement units of the further sensor, hence reducing a sensitivity of the measurement units for the vertical force.

The further sensor may comprise two measurement units, such as two strain gauges, arranged in a bridged configuration, the two measurement units being arranged, as seen in the horizontal direction orthogonal to the normal, symmetrical in respect of a median of the connecting structure, the median extending in the direction of the normal to the force transfer surface. Due to the bridging (such as in the present case a bridge, a half bridge or any other differential measurement), the effect of the vertical force on both measurement units, which effect will be substantially the same, will be cancelled by the bridging, e.g. by the differential measurement configuration.

In an embodiment, seen in the direction normal to the force transfer surface, the inner cavity of the outer handle structure exhibits a circular contour, and the outer handle structure being rotatable about the inner handle structure about the direction normal to the force transfer surface. When the user exerts a torque on the outer handle structure, the torque about the direction normal to the force transfer surfaces, decoupling of this torque from the inner handle structure is provided in that the outer handle structure is rotatable about the inner handle structure, whereby the force transfer surface of the outer handle structure is able to rotatingly slide over the force transfer surface of the inner handle structure (i.e. slide over the force transfer surface of the contact structure thereof). The outer contour of the supporting structure may, seen in the direction of the normal to the force transfer surfaces, provide a circular contour, hence on the one hand facilitating the rotation of the outer gripper structure, and on the other hand enabling force in any direction perpendicular to the normal to the force transfer surface, to be transferred from the other handle structure onto the supporting structure of the inner handle structure, hence away from the contact structure and measurement structure, causing these forces to be decoupled from the measurement of the force in the direction perpendicular to the normal, to a large extent.

The outer handle structure and the frame may comprise a mechanical interlocking to limit a freedom of rotation of the outer handle structure about the inner handle structure about the direction normal to the force transfer surface. Thus an angle of rotation of the outer handle structure in respect of the inner handle structure is limited by the mechanical interlocking. As a result, the torque on the outer handle structure is coupled to the frame by means of the interlocking, thereby further decoupling the torque from the inner handle structure, hence from the measurement of the force in the direction normal to the force transfer surfaces.

In an embodiment, an outer contour of the force measurement structure and the coupling structure in the direction normal to the force transfer surface is smaller than an inner contour of the outer handle structure, leaving a gap between the force measurement structure and the outer handle structure and a gap between the coupling structure and the outer handle structure. Hence, a direct contact and direct transfer of forces or torques may be prevented, hence promoting the above described decoupling, as undesired force transfer paths that could bypass the desired decoupling, may be avoided.

In an embodiment, an outer contour of the connecting structure in the direction normal to the force transfer surface is smaller than an inner contour of the outer handle structure, thereby leaving a gap between the connecting structure and the outer handle structure. Hence, a direct contact and direct transfer of forces or torques may be prevented, hence promoting the above described decoupling, as undesired force transfer paths that could bypass the desired decoupling, may be avoided.

In an embodiment, the normal to the force transfer surface extends in a main direction of movement of the motorized walking aid, the control unit being configured to drive the at least one electric motor to move the motorized walking aid in the main direction of movement based on the force measured by the sensor.

The motorized walking aid may comprise the further sensor and may comprise two electric motors, wherein the control unit is configured to drive the electric motors to bend away from the main direction of movement of the motorized walking aid based on a torque signal obtained from the further sensor. Hence, the user may steer the motorized walking aid in an intuitive way by exerting a torque onto the handle, which is detected by the further sensor.

The motorized walking aid may comprise two handles, one on either side of the motorized walking aid as seen in the main direction of movement, and wherein the control device is configured to further drive the electric motors to bend away from the main direction of movement of the motorized walking aid based on a difference between force signals in the main direction of movement as provided by the two handles. Using a combination of torque sensed by the further sensor, e.g. sensed by both handles, and difference in forward force between the handles, a natural feel of steering may be provided, in that a same combination of force difference and torque, which a user would normally exert on an un-motorized walking aid, cart or vehicle, in order to navigate, is applied to control the electric motor(s).

Alternatively, the control device may drive the electric motors to bend away from the main direction of movement (i.e. bend away from the straight forward direction) based on the signal from the further sensor. This may for example be useful to allow convenient steering in the case of a one handed operation.

Furthermore, the walking aid may comprise a presence sensor to detect a presence of a hand at the handle. The presence sensor may comprise any suitable type of presence sensor. For example, the presence sensor may comprise a capacitive sensor arranged in the handle, thus to detect the presence of a hand at the handle. As another example, an infrared distance sensor may be provided that detects a distance to the handle: the distance sensor may for example be arranged at another part of the walking aid, for example near the other one of the two handles, and be aimed at the handle. In case the handle is held by a hand, the hand will provide that the distance as measured by the distance sensor is reduced, as the hand covers a part of the handle, thus altering a geometric outline of the overall object formed by handle and hand. As a further example, an infrared temperature sensor may be provided that detects a body heat of a person’s hand. As a still further example, the presence sensor may comprise a heartbeat sensor arranged in (each one of) the handles. The heartbeat sensor may provide a reliable detection, as the present or absence of the heartbeat allows the control device to reliably distinguish if the force is applied by a user’s hand or originates from another source, hence being indicative of an error condition.

The control device may control the motor(s) to stop the walking aid in case no hand is sensed by the presence sensor, indicating that the user may have released his/her hands from the handle(s). Thus safety may be increased as unintended driving of the walking aid may be avoided. For example error conditions, such as a person attaching an object to the handle that may exert a force onto the handle hence providing a force signal to the control device,, may be avoided. Other error conditions such as an object pushing against the handle, etc. may be detected as well.

Furthermore, in the case of two handles, the control device may switch between operating modes in response to the signals received from the presence sensors associated with the two handles: In case the control device detects a respective hand at each handle, the control device operates in a two handed operating mode, whereby the force and/or torque signals from the two handles are taken into account to control the motor(s). In case the control device detects one hand at one handle, while the other handle is detected to be free the control device operates in a single handed operating mode, whereby the force and/or torque signals from the one handle that is held is taken into account to control the motor(s). Thus, a convenient single handed operation may be provided, for example allowing to push the walking aid in a straight line forward by exerting a forward force on tone handle with one hand. Likewise, in case the walking aid may be almost out of reach of the user, the user may conveniently pull the walking aid towards himself/herself with one hand, whereby the control device controls the electric motor(s) to move the walking aid in the direction of the user based on the force signal(s) from the one handle.

Further features, advantages and effects of the invention will follow from the enclosed drawing and the below description, showing a non-limiting embodiment of the invention, wherein:

Figure 1 depicts a schematic view of a motorized walking aid in which the invention may be employed;

Figure 2A and 2B depicts a top view and a cross sectional view of a handle according to an embodiment of the invention;

Figure 3A depicts another cross sectional view of the handle according to an embodiment of the invention;

Figure 3B depicts a detailed view of a part of Figure 3A,

Figure 4A - 4E depict side views of a part of the handle indicating measurement units in accordance with an embodiment of the invention, and

Figure 4F and 4G depict electrical diagrams of the measurement units as depicted in Figures 4A - 4C.

Throughout the figures, like reference numerals refer to the same or similar features.

Figure 1 depicts motorized walking aid MWA comprising a frame FRM, such as a metal, wood or carbon frame and wheels WLS mounted to the frame. For example, 3 or 4 wheels are provided for providing a stable walking support to the user. The motorized walking aid comprises an electric motor, e.g. one electric motor MTR per side, e.g. one electric motor at each rear wheel to drive the respective wheel. A control unit CU, such as a suitably programmed microcontroller controls the electric motors. A handle HDL is connected to the frame for enabling a user to hold himself respectively herself. As described in more detail below, the handle comprises a force sensor to sense a force exerted by the user on the handle. An output of the force sensor is connected to the control unit. The control unit is configured to control the motors using the force as sensed by the force sensor, In the present example, two handles are provided, one for each hand of the user. In another embodiment, one handle may be provided, for example one handle bar configured to be held by one or both hands of the user.

Figure 2A depicts a top view of a handle HDL and part of the frame to which the handle connects. A cross sectional view along the lines A-A of Figure 2A is depicted in Figure 2B. The outer control of the handle, seen along the line A - A is circular in the present embodiment, although other contours, e.g. following a profile of a hand, may be provided also. Figure 2B depicts the outer handle structure OHS of the handle, which forms an outer envelope thus forming the user gripping surface where the user holds the handle. The outer handle structure forms a cavity CAV in which an inner handle structure IHS is provided. The outer handle structure is in principle movable in the direction A -A, in respect of the inner handle structure and rotatable about the axis defined by A -A, in respect of the inner handle structure, although a range of movement and a range of rotation may be limited as described further below. A range of movement of the outer handle structure in respect of the inner handle structure may for example be limited to 0.1 millimetre maximum or 0.4 millimetre maximum. The former provides a good user feel with low amount of “play”, while the latter allows more relaxed manufacturing tolerances while still offering a low “play” feel to the user. It is noted that the play in the direction perpendicular to the normal to the force transfer surface is indicated in Figures 4D and 4E by 1. The play may have been exaggerated in the Figures for illustrative purpose. .

The inner handle structure comprises a supporting structure SST that supports the outer handle structure. Thereto, the supporting structure comprises bearings, in the present embodiment leaf springs LFS that support the outer handle structure at an inner face thereof,

i.e. at an inner face of the cavity. The cavity provides, seen in the direction A - A, a generally circular opening, while the support structure, in the present example the leaf springs thereof, likewise adhere to the circular outer contour. Hence, the outer handle structure is in principle movable in the direction A - A in respect of the inner handle structure by sliding or flexing of the leaf springs, while enabling the outer handle structure to in principle rotate in respect of the inner handle structure. The supporting structure is connected at one end thereof (in the direction A - A) via a connecting structure CTR to the frame. The leaf springs or other bearings where the outer handle structure contacts the inner handle structure, may be spaced apart in the direction A - A enabling the outer handle structure to transfer a torque about the direction perpendicular to the plane of drawing of Figure 2B, to the supporting structure, hence via the connecting structure to the frame. A mechanical interlocking is provided, in the present example in the form of mechanical interlocking pins MIP at the frame FRM that cooperate with a corresponding mechanical interlocking slot in the outer handle structure, thereby on the one hand limiting a rotation of the outer handle structure in respect of the frame and on the other hand transferring to the frame the torque about the direction perpendicular to the normal to the force transfer surface, as applied by the user onto the outer handle structure.

The inner handle structure further comprises a force sensing structure FSS that comprises strain gauges to measure a deformation thereof, and a coupling structure CPS. The force sensing structure is arranged between the coupling structure and the supporting structure. The coupling structure interacts with the outer handle structure by means of, in the present embodiment, a pin PN of the outer handle structure which interacts with a slit or slot in the connecting structure. The pin, where is faces the connecting structure, forms a vertical force transfer surface FTS to transfer a force in the direction A - A to the connecting structure, hence to the measuring (measurement) structure of the inner handle structure. The connecting structure likewise comprises a force transfer surface FTS that receives the force in the direction A-A.

Figure 3A depicts a top view of the inner handle structure , having the connecting structure, the supporting structure, measurement structure and the connecting structure showing the slot SLT in the connecting structure as well as, in Figure 3B, a cross sectional view of the pin of the outer handle structure arranged in the slot. At the connecting structure, a recess RCS is provided extending through the connecting structure in the vertical direction to allow some resiliency of this part of the inner connecting structure about the vertical axis. A further sensor, in the form of strain gauges, is provided at the connecting structure, so as to be able to measure a force acting on the handle in sideward direction, e.g. in horizontal direction perpendicular to the line A - A as well as torque about on the handle about the vertical direction. In the present example, the torque resp. force is measured by strain gauges forming the further sensor FSR.

Figure 4A depicts a side view of the inner handle structure, showing the connecting structure with strain gauges (measurement units) G, the supporting structure, the measurement structure and connecting structure. Also, the pin of the outer measurement structure is depicted.

Figures 4B and 40 depict top and bottom views of a part of the handle, namely the inner handle structure, while Figure 4D and 4E depict left and fight side views of the same. A positioning of the measurement units (strain gauges) G1 - G8 is depicted in Figures 4B - 4E. The strain gauges G1 - G4 are comprised in the sensor, the strain gauges G5 - G8 are comprised in the further sensor. A measurement bridge of the sensor is depicted in Figure 4F while a measurement bridge of the further sensor is depicted in Figure 4G. In the sensor, strain gauges G1 and G3 provide for measurement information, while strain gauges G2 and G4 provide for temperature compensation. Similarly, in the further sensor, strain gauges G5 and G6 provide for measurement information, while strain gauges G7 and G8 provide for temperature compensation. For example, a measurement signal may be applied at terminals D and G of the bridge, while a readout amplifier input may connected to terminals E and F. The bridge configuration and the placement of the measurement units further provides for a degree of decoupling: For example, strain gauges G1 and G3 are arranged on opposite sides at the force sensing structure FSS. In case a force in the forward direction, i.e. the perpendicular to the force transfer surface, is applied, both G1 and G3 are subject to a similar deformation. In the bridge configuration, G1 and G3 are each connected in a branch of the bridge network, whereby G1 is arranged in the upper part one branch and G3 in the lower part of the other branch, hence the result of both contributes to a bridge output voltage. Conversely, a vertical force may result in opposite deformations of G1 and G3, which will to a large part cancel each other in the bridge. Furthermore, a torque about the vertical axis will deform both G1 and G3 is a similar way, however the deformations will, on one side of a centre axis of the inner handle structure, provide for a stretching and on the other side of the inner handle structure, provide for a compression (squeezing), thus a net result the resistance of the strain gauges G1, G3 substantially remaining the same. Similar considerations apply to strain gauges G5 and G6. For example, strain gauges G5 and G6 are arranged on opposite left and right sides at the inner handle structure. In case a force in the sideward direction is applied, G5 and G6 are subject to a opposite deformation. In the bridge configuration, G5 and G6 are each connected in a branch of the bridge network, whereby both G5 and G6 is arranged in the upper part of the branches, hence the result of both contributes to a bridge output voltage. Conversely, a horizontal, forward force may result in the same deformations of G5 and G6, which will to a large part cancel each other in the bridge due to symmetric circuit branches in the bridge. Furthermore, a torque about the vertical axis will deform both G5 and G5 is a similar way, however the deformations will, on one side of a centre axis of the inner handle structure, provide for a stretching and on the other side of the inner handle structure, provide for a compression (squeezing), thus a net result the resistance of the strain gauges G5, G6 substantially remaining the same. Readout electronics of the strain gauges may be arranged in the inner handle structure, hence providing for short electrical connections of the strain gauges thus reducing sensitivity to disturbances, such as electromagnetic disturbances. Furthermore, the outer handle structure may be formed as a metal part, thus providing for a shielding.

The influence of the downward force on the forward I backward force measurement can be decoupled in a classic way by strain gauge wiring, however in the present context the difference between the forward I downward force is too large. So that this solution cannot decouple the vertical force sufficiently. Therefore the inner handle structure is connected to the outer handle structure by the pin that can move freely up and down in the slit in the inner handle structure, while the pin forms part of resp. is fixed to, the outer handle structure. Consequently, the outer handle structure can move up and down to some extent without effecting the forward and backward force measurement, as the force transfer surface of the pin slides over the force transfer surface of the slot. By moving forward/backward the outer handle structure exerts a forward I backward force to the inner handle structure, as the pin from the outer handle structure presses against the force transfer surface in the measurement structure of the inner handle structure. Strain gauges at the inner handle structure measure this forward I backward force. The slot in the inner handle structure defines a range of movement of the outer handle structure in respect of the handle structure. This range is preferably 0,1 millimetre maximum or 0,4 millimetre maximum as specified above. If it is too big, the outer handle structure has to move significantly before the pin will touch the inner handle structure. If it is too small, the pin will have a press fit with the slot so it cannot freely move up and down without affecting the forward and backward force measurement.

The second way the downward force can affect the forward I backward force measurement is by the influence of friction between the inner handle structure and outer handle structure. The forward / backward force measurement is at the user end of the inner handle structure, so if there is friction between the supporting structure of the inner handle structure and the outer handle structure, i.e. more towards the end where the handle is attached to the frame, it will transfer that forward / backward force directly to the supporting structure of the inner handle structure, hence this bypassed force (or force part) is measured by the sensor in the measurement structure. If the user exerts more downwards force the friction force will become bigger. Due to the fact that the downward force is so much bigger than the forward force, static friction would bypass at least part of the forward force. Accordingly, the leaf spring bearing is provided so that, if there is too much downward force, the outer handle structure will not slide over the bearings but will bend forward and when the forward force is removed it will bend back. When there is not much downward force then the outer tube is able to slide over the bearing blocks. These blocks may made from nylon with a good friction coefficient. The size of these bearing blocks will provide for a fit of the outer handle structure, while preventing too much play between the inner and outer handle structure as to much play would result in a strange feel for the user.

A sideward force can also influence the forward / backward force in the same way as the downward force, albeit that the sideward force may in practice be lower than the downward force so there may be less problems with this. In the end of the handle where the forward / backward force is measured the slot with pin construction provides for a play in the horizontal direction perpendicular to the forward/backward direction, thus the pin can move from left to right. Due to the play in sideward direction, these sideward forces are not transferred to the part where the forward I backward force is measured. The friction with the inner tube is solved by the same bearing blocks solution. Due to the fact these bearing blocks are round and have the same diameter as the inside of the outer handle structure, it is refrained from moving from left to right and can only touch the bearing blocks. However, the leave springs are not effected by sideward forces and will hence directly transfer this force from the bearing blocks to the inner tube at the places where the bearings are mounted.

Rotation of the outer handle structure can also effect the forward / backward force if it transferred to the user side of the handle where the forward I backward force is measured. However, the outer handle structure can rotate over the bearing blocks. Due to the pin and slot construction where the pin is going through freely given the sideward play of the pin in the slot, the handlebar can rotate a bit (20 degrees) left and right without effecting the forward and backward force measurement. For bigger rotations it will and hence to make sure the handle cannot rotate freely and has a steady feel there are pins in the front of the handle (towards the frame) on the top and on the bottom. These pins on the inner handle structure are smaller than the slots in the outer handle structure, so the outer handle structure may have no problem with the forward and backwards direction. However when rotation is applied on the handle(s), the holes in the outer handle structure will touch the pins from the inner handle structure and prevent it from rotating. The holes and pins thereby form an example of a mechanical interlocking. The pins are in the front of the handlebar towards the frame, so they do not affect the sideward and forward I backward force measurement and directly transfer the force to the frame.

The handles as described above are mounted to the frame such that the direction A-A coincides with a main direction of movement of the motorized walking aid, i.e. the forward direction. The direction A -A, hence in the present example the forward direction of movement, forms a normal to the force transfer surfaces. Thus, a high degree of decoupling may be provided, as forces in other direction may provide for some sliding of the force transfer surfaces in respect of each other (i.e. movement along the plane of the surfaces) enabling to accurately control a support by the motor of the motorized walking aid based on a force exerted on the handle in the forward direction, even in the presence of high forces in other directions, such as forces as a result of the person leaning on the handles for support.

The control unit may provide for a drive of the electric motors, i.e. torque of the electric motors proportional to the force in the horizontal direction, as measured by the handle(s). For example, as sum or average of the forces measured by the two handles may be applied to determine a forward walking support motor torque. The further sensors may provide signals to the control unit to steer the motorized walking aid, e.g. to bend away from the main (forward) direction of movement. The steering may either be performed based on the measured sideward forces and torque about the vertical axis as exerted by the user on the handles, or, for a more natural feeling of handling, a combination of this sideward force and torque about the vertical axis on the one hand and a difference between the forward forces on the two handles, may be applied. The use of the difference between the forward forces on the two handles may be de-activated by the control unit in case the control unit notes that one handle is left unused, i.e. the sensor and/or further sensor of this handle does not measure any force. This condition would indicate that the user only operates the walking support with one hand, which may be the case because of impairment, revalidation or because one handle is presently out of reach of the person. Thus, in case one handle is left at rest, the control unit applied the forward/backward force of the other handle for forward/backward drive control and applies the signal received by the further sensor for steering.

The walking aid may comprise a presence sensor to detect a presence of a hand at the handle. The presence sensor may for example comprise a capacitive sensor arranged in the handle, an infrared temperature sensor that detects a body heat of a person’s hand, a heartbeat sensor arranged in (each one of) the handles, or an infrared distance sensor aimed at the handle to detects a free air distance to the handle, which distance will reduce when the handle is held by a hand. The control device may control the motor(s) to stop the walking aid in case no hand is sensed by the presence sensor, indicating that the user may have released his/her hands from the handle(s). Furthermore, in the case of two handles, the control device may select an operating mode in response to the signals received from the presence sensors associated with the two handles: In case the control device detects a respective hand at each handle, the control device operates in a two handed operating mode, whereby the force and/or torque signals from the two handles are taken into account to control the motor(s). In case the control device detects one hand at one handle, while the other handle is detected to be free, the control device operates in a single handed operating mode, whereby the force and/or torque signals from the one handle that is held is taken into account to control the motor(s), while any signal from the force sensor and/or further force sensor in the other handle may be disregarded.

The electric motor(s) may comprise any suitable electric motor, such as a stepper motor, a brushless DC motor, etc.

Although the above example describe force transfer surfaces as a pin and a slot, many alternatives are possible. For example, the outer handle structure may comprise a vertical surface at an end of the handle, and facing the cavity. The coupling structure of the inner handle structure may provide a vertical force transfer surface that faces the force transfer surface of the outer handle structure, to transfer a force in the forward direction from the outer handle structure via the mutually contacting, parallel force transfer surfaces to the inner handle structure.

Claims

CONCLUSIONS

A motorized walking aid comprising a frame, wheels mounted on the frame, at least one motor for driving the wheels, a control unit for controlling the at least one motor and a handle connected to the frame for possible causing a user to hold on to himself, the handle including a force sensor for measuring a force exerted by the user on the handle, an output of the force sensor being connected to the control unit, the control unit being adapted to control the at least one motor using the force as measured by the force sensor, the handle comprising:

an outer handle structure comprising a user gripping surface on an outer side thereof and defining an inner cavity, and an inner handle structure extending into the inner cavity, the inner handle structure comprising:

o a support structure that supports the outer handle structure and having a first end and a second end opposite to the first end, o a connection structure arranged between the first end of the support structure and the frame and which connects the support structure to the frame, o a force measurement structure comprising the force sensor, wherein the force measurement structure is adapted to measure a force between a first end and a second end thereof, the first end of the force measurement structure being connected to the second end of the support structure, and a connection structure which is connected is with the second end of the force measurement structure, the connection structure comprising a force transmission surface, the outer handle structure comprising a force transmission surface arranged substantially parallel to and facing the force transmission surface of the connection structure, wherein the outer handle structure is movable with respect to the inner handle structure in a direction normal to the force transmission surfaces, the outer handle structure being adapted to transfer via the force transmission surface thereof to the force transmission surface of the connection structure a force which is applied by the user to the

-21 outer handle structure is normally exerted on the force transmission surfaces in a first direction, the force transmission surface of the outer handle structure being slidable relative to the force transmission surface of the contact structure.

Motorized walking aid according to claim 1, wherein the normal on the force transmission surface extends in a main direction of movement of the motorized walking aid.

3. Motorized walking aid as claimed in claim 1 or 2, wherein the force transmission surfaces extend in a vertical direction, and wherein the force transmission surface of the outer handle structure is slidable in the vertical direction relative to the force transmission surface of the contact structure.

A motorized walking aid according to any one of the preceding claims, wherein the support structure comprises bearings which support the outer handle structure on the inner surface thereof, the bearings showing a spring force in the direction normally on the force transmission surface.

5. Motorized walking aid as claimed in any of the foregoing claims, wherein the connecting structure and the outer handle structure comprise mutually facing further force transmission surfaces which are arranged substantially parallel to the force transmission surfaces, wherein the outer handle structure is adapted for transferring from the further force transmission surface to the connection structure a force exerted by the user on the outer handle structure in a direction normal to the force transmission surface and perpendicular to the first direction.

6. Motorized walking aid as claimed in any of the foregoing claims, wherein the force sensor comprises two units of measurement arranged in a bridge configuration, the two units of measurement arranged, viewed in the vertical direction, symmetrical with respect to a median of the measurement structure, the median extends in the direction of the normal to the force transmission surface.

Motorized walking aid as claimed in any of the foregoing claims, wherein in a horizontal direction orthogonal to the normal to the force transmission surface a stiffness of the connecting structure is lower than a stiffness of the supporting structure, wherein a further sensor is attached to the connecting structure

-22 applied to measure a torque about a vertical direction on the support structure.

Motorized walking aid according to claim 7, wherein, viewed in the vertical direction, the further sensor is arranged on a median of the connection structure.

9. Motorized walking aid as claimed in claim 7 or 8, wherein the further sensor comprises two measuring units arranged in a bridge configuration, wherein the two measuring units, viewed in the horizontal direction are arranged orthogonally on the normal, symmetrical with respect to a median of the connecting structure wherein the median extends in the direction of the normal on the force transmission surface.

Motorized walking aid according to one of the preceding claims, wherein, viewed in the direction normal on the force transmission surface, the inner cavity of the outer handle structure shows a circular contour, and wherein the outer handle structure is rotatable about the inner handle structure on the direction normal on the force transmission surface.

A motorized walking aid according to claim 10, wherein the outer contour of the support structure, viewed in the direction of the normal on the force transmission surfaces, can have a circular contour.

A motorized walking aid according to claim 10 or 11, wherein the outer handle structure and the frame comprise a mechanical mutual engagement for limiting a freedom of rotation of the outer handle structure about the inner handle structure about the direction normally on the force transmission surface.

A motorized walking aid according to any one of the preceding claims, wherein an outer contour of the force measuring structure and the connecting structure in the direction normally on the force transmission surface is smaller than an inner contour of the outer handle structure, wherein an opening between the force measuring structure and the outer handle structure and an opening between the connection structure and the outer handle structure is left.

A motorized walking aid according to any one of the preceding claims, wherein an outer contour of the connecting structure in the direction normally on the force transmission surface is smaller than an inner contour of the

-23 outer handle structure, leaving an opening between the connection structure and the outer handle structure.

Motorized walking aid according to one of the preceding claims, wherein the normal on the force transmission surface extends in a main direction of movement of the motorized walking aid, wherein the control unit is adapted to drive the at least one electric motor for moving the motorized walking aid. walking assistance in the main direction of movement based on the force measured by the sensor.

A motorized walking aid according to claim 15, comprising the further sensor and comprising two electric motors, wherein the control unit is adapted to drive the electric motors for deflecting the main direction of movement of the motorized walking aid based on a torque signal that of the further sensor has been obtained.

A motorized walking aid according to claim 15 or 16, comprising two handles, one on each side of the motorized walking aid as viewed in the main direction of movement, and wherein the control device is adapted to further drive the electric motors for deflecting the main direction of movement of the motorized walking aid based on a difference between force signals in the main direction of movement as provided by the two handles.

A motorized walking aid according to any one of the preceding claims, further comprising a presence sensor adapted to detect the presence of a hand on the handle.

A motorized walking aid according to claim 18, comprising two handles, wherein the control device is adapted to operate in a one-handed operating mode in which the electric motors are driven based on the force signal received from the force sensor in one of the handles, and for working in a two-handed operation mode where the electric motors are driven based on the force signals received from the force sensors in the two handles, the control device being adapted to select the one-handed operation mode in case one hand is detected by the presence sensor and to select the two-handed operation operating mode in case two hands are detected by the presence sensor.

WLS