Method of setting seat and / or drive characteristics restrictions for a power wheelchair

Abstract

A method of setting one or more seating system and / or drive characteristics restrictions for a power wheelchair comprising a chassis, a seating system comprising a lift and tilt device mounted to the chassis and a seat assembly mounted to the lift and tilt device, the method comprising: a) determining a lift position and a tilt position of the lift and tilt device, b) determining an inclination angle and a roll angle of the power wheelchair, c) determining a centre of mass location of the power wheelchair with its intended wheelchair occupant based on the lift position, the tilt position, the inclination angle, and the roll angle, and further based on a chassis mass and centre of mass of the chassis, a seat assembly mass and a centre of mass of the seat assembly, a lift and tilt device mass, and a mass of the intended wheelchair occupant, and d) setting the one or more seating system and / or drive characteristics restrictions based on the centre of mass location.

Description

[0001] METHOD OF SETTING SEAT AND / OR DRIVE CHARACTERISTICS RESTRICTIONS FORA POWER WHEELCHAIR

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to power wheelchairs.

[0004] BACKGROUND

[0005] The limits for seat stability parameters of wheelchairs, such as tilt angle or seat elevation when a wheelchair is stationary, or static, and dynamic, or drive, stability parameters of wheelchairs, such as speed and acceleration / deceleration in combination with the seat stability parameters, is commonly set in increments. The number of increments is low due to the large number of tests that need to be carried out to find the limits for each combination of seat position and user weight. The result is a very low resolution of the restriction increments. The user weight may for example be divided into a number of ranges such as 70-99 kg, 100-135 kg and so on, resulting in the same settings and restrictions for a user in the bottom of a weight span as for a user in the top of the weight span. Furthermore, the restrictions may often be based on the assumption that the wheelchair is positioned with the maximum inclination according to test methods defined by the relevant ISO and Resna standards. The static and dynamic restrictions for a wheelchair may thus be set as if the inclination was ±9° or ±12° even if the wheelchair is oriented completely horizontal.

[0006] SUMMARY

[0007] A general object of the present disclosure is to provide a method of setting one or more seating system and / or drive characteristics restrictions for a power wheelchair which solves or at least mitigates the problems of the prior art.

[0008] There is hence according to a first aspect of the present disclosure provided a method of setting one or more seating system and / or drive characteristics restrictions for a power wheelchair comprising a chassis, a seating system comprising a lift and tilt device mounted to the chassis and a seat assembly mounted to the lift and tilt device, the method comprising: a) determining a lift position and a tilt position of the lift and tilt device, b) determining an inclination angle and a roll angle of the power wheelchair, c) determining a centre of mass location of the power wheelchair with its intended wheelchair occupant based on the lift position, the tilt position, the inclination angle, and the roll angle, and further based on a chassis mass and centre of mass of the chassis, a seat assembly mass and a centre of mass of the seat assembly, a lift and tilt device mass, and a mass of the intended wheelchair occupant, and d) setting the one or more seating system and / or drive characteristics restrictions based on the centre of mass location.

[0009] The seating system and / or the drive characteristics may thus be set much more precisely, adapted to the actual conditions with regards to the power wheelchair and its intended occupant. For example, the drive speed, being an example of a drive characteristic restriction, maybe set with e.g., 1% increments instead of for example only four different steps as could be the case in the state-of-the-art solutions. Moreover, the usage of the seat geometry of the seating system may be improved. According to simulations by the applicant, the usage of the seat geometry may be improved with over 25%. There is for example no need to restrict movement of the seat assembly when the power wheelchair is level. Furthermore, it allows for the user to drive faster in an elevated seat position. Moreover, because the seating system and / or drive characteristics restrictions are determined based on the mass of the intended wheelchair occupant, and not on predefined ranges, all users enjoy the same margin of safety.

[0010] The method may be carried out over and over again when the power wheelchair is in an on state. Thus, steps a)-d) maybe repeated over and over again when the power wheelchair is in the on state.

[0011] The method may be carried out in real-time when the power wheelchair is in the on state. According to one embodiment the seating system comprises a leg rest, and the method comprises determining a leg rest angle of the leg rest, wherein the determining in step c) is further based on a leg rest mass and the leg rest angle.

[0012] According to one embodiment the seating system characteristics restrictions include a maximum leg rest angle and a minimum leg rest angle.

[0013] According to one embodiment the power wheelchair comprises a leg rest actuator for controlling the leg rest angle, wherein the method comprises determining a leg rest actuator position of the leg rest actuator, and wherein the leg rest angle is determined based on the leg rest actuator position.

[0014] According to one embodiment the determining in step c) further comprises determining a centre of mass of a wheelchair accessory attached to the power wheelchair, wherein the determining in step c) is further based on the centre of mass of the wheelchair accessory, and on a mass of the wheelchair accessory.

[0015] According to one embodiment the seating system comprises a backrest, wherein the method comprises determining a backrest recline position, wherein the determining in step c) is further based on the backrest recline position.

[0016] According to one embodiment the power wheelchair comprises a backrest actuator for controlling the backrest recline position, wherein the method comprises determining a backrest actuator position of the backrest actuator, and wherein the backrest recline position is determined based on the backrest actuator position.

[0017] According to one embodiment the seating system characteristics restrictions include a maximum backrest recline angle and a minimum backrest recline angle. The maximum backrest recline angle is achieved when the backrest is maximally reclined. One embodiment comprises determining a centre of mass of the intended wheelchair occupant in accordance with ISO 7176-11:2012 (E) based on the mass of the intended wheelchair occupant, wherein the determining in step c) is further based on the determined centre of mass of the intended wheelchair occupant.

[0018] It is envisaged that as an alternative, the centre of mass of the intended wheelchair occupant may be determined in accordance with another standard than ISO 7176-11:2012 (E) or a newer version of this ISO-standard, based on the mass of the intended wheelchair occupant.

[0019] One embodiment comprises determining a centre of mass of the intended wheelchair occupant based on the mass of the intended wheelchair occupant and an estimated or stated weight distribution of the intended wheelchair occupant, wherein the determining in step c) is further based on the determined centre of mass of the wheelchair occupant.

[0020] According to one embodiment the determining in step c) is further based on a wheelbase of the power wheelchair.

[0021] According to one embodiment the power wheelchair comprises lift and tilt device actuators for controlling the lift position and the tilt position, wherein step a) comprises determining actuator positions of the lift and tilt device actuators, and wherein the lift position and the tilt position are determined based on the actuator positions.

[0022] According to one embodiment the seating system characteristics restrictions include a maximum lift height, a minimum tilt angle, and a maximum tilt angle. The maximum tilt angle is achieved when the lift and tilt device is maximally tilted posteriorly. The seat assembly is in this case thus tilted maximally posteriorly, i.e., backwards.

[0023] The maximum lift height is a parameter of the lift and tilt device. The maximum lift height thus sets the maximum extension of lift provided by the lift and tilt device. The maximum lift height also affects the seat assembly mounted to the lift and tilt device.

[0024] According to one embodiment the drive characteristics settings include a maximum driving speed and / or maximum braking force.

[0025] According to one embodiment step d) involves setting the maximum driving speed with a resolution of at most io% increments, such as at most 5% increments, such as at most 1% increments, in a range of 0-100% of the rated top speed of the power wheelchair.

[0026] According to one embodiment step b) involves determining the inclination angle and the roll angle by means of an inertial measurement unit.

[0027] There is according to a second aspect of the present disclosure provided a power wheelchair comprising: a chassis, a seating system comprising: a lift and tilt device mounted to the chassis, and a seat assembly mounted to the lift and tilt device; and a control system configured to perform the method of the first aspect.

[0028] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means”, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, etc., unless explicitly stated otherwise.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which:

[0031] Figs 1-2 are graph depicting speed restriction curves;

[0032] Fig. 3 is a perspective view of an example of a power wheelchair; Fig. 4 is a block diagram of certain units / components of a power wheelchair; and

[0033] Fig. 5 is a flowchart of a method of setting one or more seating system and / or drive characteristics restrictions for a power wheelchair.

[0034] DETAILED DESCRIPTION

[0035] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept 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 by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

[0036] Fig. i is a graph depicting an example of a first speed restriction curve Ci of a prior art solution and a second speed restriction curve C2 achievable by means of the present disclosure, for power wheelchairs comprising a seat assembly and a seat lift that can change the vertical position of the seat assembly. The x-axis denotes the speed of a power wheelchair, and the y-axis denotes the lift height.

[0037] As the lift height increases, the speed limit according to the prior art solution is reduced from smax, which may be the maximum driving speed of the power wheelchair at no lift height, in discrete steps. At a lift height hi, which is larger than the no lift height, the maximum speed is reduced to speed si, with si<smax, and at lift height h2, with h2>hi, the maximum speed is reduced further to a maximum speed S2, with s2<si. The increments by means which the maximum speed is reduced for different lift heights are very large, and thus the resolution is very coarse with only a few steps, in the order of 20-25% speed reduction per step, are available.

[0038] By means of the present disclosure, because amongst other things, the actual lift position, tilt position, inclination angle, and roll angle of the power wheelchair are determined, and because the mass of the intended wheelchair occupant is used as basis to determine drive characteristics restrictions of the power wheelchair, the second speed restriction curve C2, which is much smoother than the first speed restriction curve Ci, may be achieved. Here, the increments at which the maximum speed is set may be made much smaller, for example in 1% increments. Moreover, the second speed restriction curve C2 may be shifted to the right as shown in Fig. 2, meaning that the instances at which the speed limit is restricted may be shifted to start at higher lift heights than in prior art solutions. That the second speed restriction curve C2 is shifted to the right means that the centre of mass location of the power wheelchair is moved rearwards / downwar ds if for example the backrest is reclined.

[0039] Fig. 3 is a perspective view of an example of a power wheelchair i. The depicted power wheelchair i is a front wheel drive wheelchair, but could alternatively be e.g., a midwheel drive or a rearwheel drive power wheelchair.

[0040] The power wheelchair 1 comprises a chassis 3. The power wheelchair 1 may comprise a battery pack (not shown) for example arranged in, provided on, or underneath the chassis 3.

[0041] The power wheelchair 1 may comprise swing arms 5 pivotably connected to the chassis 3. The power wheelchair 1 may comprise caster wheels 7 connected to a respective swing arm 5.

[0042] The power wheelchair 1 comprises drive wheels 8 rotatably connected to the chassis 3, either by drive wheel swing arms or directly.

[0043] The power wheelchair 1 furthermore comprises electric motors. Each electric motor is configured to drive a respective drive wheel 8.

[0044] The power wheelchair 1 comprises a seating system 9. The seating system 9 maybe mounted to the chassis 3. The seating system 9 includes a seat assembly. The seat assembly may include a seat base 11a, a seat 11b mounted to the seat base 11a, and a backrest 11c.

[0045] The seating system may comprise a leg rest nd. The leg rest nd may be configured to pivot relative to the chassis 3.

[0046] Fig. 4 is a block diagram of certain units / components of the power wheelchair 1. The seating system 9 includes a lift and tilt device 9a. The lift and tilt device 9a maybe mounted to the chassis 3. The seat assembly maybe mounted to the lift and tilt device 9a. In particular, the seat base 11a maybe mounted to the lift and tilt device 9 a.

[0047] The power wheelchair 1 may comprise one or more lift and tilt device actuators 12 configured to control a lift position and tilt position of the lift and tilt device 9a relative to the chassis 3. The lift and tilt device 9a is configured to set a lift position of the seat assembly relative to the chassis 3. The lift and tilt device 9a is configured to set a tilt position of the seat assembly relative to the chassis 3. The tilt position may for example be an anterior tilt position or a posterior tilt position.

[0048] The leg rest nd may be pivotably connected to the lift and tilt device 9 a or to the seat base 11a, for example.

[0049] The backrest 11 may for example be pivotably connected to the lift and tilt device 9a or to the seat base 11a.

[0050] The power wheelchair 1 may comprise a leg rest actuator 14 configured to control a leg rest angle of the leg rest nd. The leg rest angle is a pivot angle of the leg rest nd relative to the lift and tilt device 9a or the seat base 11a to which the leg rest nd may be pivotably connected.

[0051] The power wheelchair 1 may comprise one or more backrest actuators 16 configured to control a backrest recline position of the backrest 11c. The power wheelchair 1 may further comprise an inertial measurement unit 13 configured to determine an inclination angle and a roll angle of the power wheelchair 1.

[0052] The power wheelchair 1 may comprise a control system 15. The control system 15 may be configured to control all the actuators of the power wheelchair 1, e.g., the lift and tilt device actuator(s) 12, the leg rest actuator 14, and / or the one or more backrest actuators 16.

[0053] The lift and tilt device actuator(s) 12, the leg rest actuator 14, and / or the one or more backrest actuators 16 may be linear actuators.

[0054] The control system 15 may be configured to receive measurement signals generated by the inertial measurement unit 13.

[0055] The power wheelchair 1 may comprise means, including e.g., position sensors, current sensors, or encoders or the like, that generate signals which allows the control system 15 to determine the position of the actuators, e.g., the lift and tilt device actuator(s) 12, the leg rest actuator 14, and / or the one or more backrest actuators 16.

[0056] The control system 15 is configured to determine and set seating system and / or drive characteristics restrictions based on the signal from the inertial measurement unit 13, based on the lift and tilt position of the lift and tilt device 9a, based on the mass and centre of mass of various components, and based on the mass of the intended wheelchair occupant, as will be explained in more detail with reference to Fig. 5 in the following.

[0057] Fig. 5 is a flowchart of a method of setting one or more seating system and / or drive characteristics restrictions for the power wheelchair 1.

[0058] The seating system characteristics restrictions may include a maximum lift height of the lift and tilt device 9a, a minimum tilt angle of the lift and tilt device 9a, and a maximum tilt angle of the lift and tilt device 9a. The seating system characteristics restrictions may include a maximum leg rest angle and a minimum leg rest angle.

[0059] The drive characteristics settings may include a maximum driving speed and / or maximum braking force of the power wheelchair 1.

[0060] In a step a) a lift position and a tilt position of the lift and tilt device 9a is determined. Hereto, the control system 15 may determine the lift position and the tilt position, for example based on a position or positions of the lift and tilt device actuator(s) 12.

[0061] In a step b) an inclination angle and a roll angle of the power wheelchair 1 is determined. The inclination angle and the roll angle may be determined based on measurements from the inertial measurement unit 13.

[0062] In a step c) a centre of mass location of the power wheelchair 1 with its intended wheelchair occupant is determined. The centre of mass location is determined based on the lift position, the tilt position, the inclination angle, and the roll angle. Further, the centre of mass location is additionally based on a chassis mass and centre of mass of the chassis 3, a seat assembly mass and a centre of mass of the seat assembly, a lift and tilt device mass, and a mass of the intended wheelchair occupant. The centre of mass location may further be determined based on a centre of mass of the lift and tilt device.

[0063] The chassis mass is the mass of the chassis 3 and it is predefined, i.e., known from the model of the power wheelchair 1. The same applies also for the seat assembly mass and the lift and tilt device mass. The centre of mass of the chassis, the lift and tilt device mass, the centre of mass of the lift and tilt device, and the centre of mass of the seat assembly is also predefined.

[0064] One example comprises determining a leg rest angle of the leg rest nd. The determining in step c) is in this case further based on a leg rest mass and the leg rest angle. The leg rest mass maybe predefined, i.e., known from the model of the power wheelchair 1. The control system 15 may determine a leg rest actuator position and based on the leg rest actuator position determine the leg rest angle.

[0065] One example comprises determining a backrest recline position. The determining in step c) is in this case further based on the backrest recline position. The control system 15 maybe configured to determine the backrest recline position based on a backrest actuator position of the backrest actuator 16.

[0066] A mathematical model of the seat assembly or the seating system may be used for calculating e.g., the leg rest angle and the backrest recline position.

[0067] One example comprises determining a centre of mass of a wheelchair accessory attached to the power wheelchair 1. The wheelchair accessory may for example be an oxygen tank, a ventilator, or a backpack. The wheelchair accessory has a predefined mass and shape, allowing for determining the centre of mass of the wheelchair accessory. Hereto, the control system 15 may for example be configured to determine the centre of mass of the wheelchair accessory. The determining in step c) may further be based on the centre of mass of the wheelchair accessory, and on a mass of the wheelchair accessory.

[0068] In one example the determining in step c) is further based on a wheelbase of the power wheelchair 1.

[0069] The intended wheelchair occupant is the user for which the power wheelchair 1 has been configured.

[0070] The centre of mass of the intended wheelchair occupant may for example be determined in accordance with ISO 7176-11:2012 (E) based on the mass of the intended wheelchair occupant. The determining in step c) is further based on the determined centre of mass of the intended wheelchair occupant.

[0071] The mass of the intended wheelchair occupant may for example be set with 1 kg increments. In one example, a centre of mass of the intended wheelchair occupant may be determined based on the mass of the intended wheelchair occupant and an estimated or stated weight distribution of the intended wheelchair occupant. The estimated or stated weight distribution of the intended wheelchair occupant may according to one example be determined according to ISO 7176-11:2012 (E). Alternatively, the estimated or stated weight distribution maybe set to correspond to that of an individual user, i.e., of the intended wheelchair occupant instead of using a weight distribution defined by a standard such as ISO 7176-11:2012 (E). The estimated or stated weight distribution then takes into account the actual weight distribution of the intended wheelchair occupant. Thus, for example if the intended wheelchair occupant lacks legs, this is reflected by the estimated weight distribution. The location of the centre of mass of the intended wheelchair occupant may according to one example be determined according to ISO 7176-11:2012 (E) or based on a dedicated mathematical model of the weight distribution of the intended wheelchair occupant. The determining in step c) may further be based on the determined centre of mass of the wheelchair occupant.

[0072] In one example, a current consumption of actuators, i.e., the lift and tilt device actuator(s) 12, the leg rest actuator 14, and / or the one or more backrest actuators 16 at a predefined speed and position is measured continually to obtain an estimate of the mass of the intended wheelchair occupant. The estimate of the mass of the intended wheelchair occupant may be used in step c) to determine the centre of mass location of the power wheelchair 1. The purpose is to detect if the mass of the intended wheelchair occupant changes over time or if extra weight is added in the form of e.g., a wheelchair accessory.

[0073] In a step d) the one or more seating system and / or drive characteristics restrictions is / are set based on the centre of mass location of the power wheelchair 1 determined in step c).

[0074] According to one example, step d) involves setting the maximum driving speed with a resolution of at most 10% increments, such as at most 5% increments, such as at most 1% increments, in a range of 0-100% of the rated top speed of the power wheelchair 1. The resolution may thus be made essentially as small as desired e.g., to obtain an almost continuous adaptation of the one or more seating system and / or drive characteristics restrictions of the power wheelchair 1.

[0075] The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.

Claims

CLAIMS1. Method of setting one or more seating system and / or drive characteristics restrictions for a power wheelchair (1) comprising a chassis (3), a seating system (9) comprising a lift and tilt device (9a) mounted to the chassis (3) and a seat assembly mounted to the lift and tilt device (9a), the method comprising: a) determining a lift position and a tilt position of the lift and tilt device (9a), b) determining an inclination angle and a roll angle of the power wheelchair (1), c) determining a centre of mass location of the power wheelchair (1) with its intended wheelchair occupant based on the lift position, the tilt position, the inclination angle, and the roll angle, and further based on a chassis mass and centre of mass of the chassis, a seat assembly mass and a centre of mass of the seat assembly, a lift and tilt device mass, and a mass of the intended wheelchair occupant, and d) setting the one or more seating system and / or drive characteristics restrictions based on the centre of mass location.

2. Method as claimed in claim 1, wherein the seating system (9) comprises a leg rest (nd), and the method comprises determining a leg rest angle of the leg rest (nd), wherein the determining in step c) is further based on a leg rest mass and the leg rest angle.

3. Method as claimed in claim 2, wherein the seating system characteristics restrictions include a maximum leg rest angle and a minimum leg rest angle.

4. Method as claimed in claim 2 or 3, wherein the power wheelchair (1) comprises a leg rest actuator (14) for controlling the leg rest angle, wherein the method comprises determining a leg rest actuator position of the leg restactuator (14), and wherein the leg rest angle is determined based on the leg rest actuator position.

5. Method as claimed in any of the preceding claims, wherein the determining in step c) further comprises determining a centre of mass of a wheelchair accessory attached to the power wheelchair (1), wherein the determining in step c) is further based on the centre of mass of the wheelchair accessory, and on a mass of the wheelchair accessory.

6. Method as claimed in any of the preceding claims, wherein the seating system (9) comprises a backrest (11c), wherein the method comprises determining a backrest recline position, wherein the determining in step c) is further based on the backrest recline position.

7. Method as claimed in claim 6, wherein the power wheelchair comprises a backrest actuator (16) for controlling the backrest recline position, wherein the method comprises determining a backrest actuator position of the backrest actuator (16), and wherein the backrest recline position is determined based on the backrest actuator position.

8. Method as claimed in claim 6 or 7, wherein the seating system characteristics restrictions include a maximum backrest recline angle and a minimum backrest recline angle.

9. Method as claimed in any of the preceding claims, comprising determining a centre of mass of the intended wheelchair occupant in accordance with ISO 7176-11:2012 (E) based on the mass of the intended wheelchair occupant, wherein the determining in step c) is further based on the determined centre of mass of the intended wheelchair occupant.

10. Method as claimed in any of claims 1-8, comprising determining a centre of mass of the intended wheelchair occupant based on the mass of the intended wheelchair occupant and an estimated or stated weight distribution of the intended wheelchair occupant, wherein the determining in step c) is further based on the determined centre of mass of the wheelchair occupant.1611. Method as claimed in any of the preceding claims, wherein the determining in step c) is further based on a wheelbase of the power wheelchair (i).

12. Method as claimed in any of the preceding claims, wherein the power wheelchair (1) comprises lift and tilt device actuators (12) for controlling the lift position and the tilt position, wherein step a) comprises determining actuator positions of the lift and tilt device actuators (12), and wherein the lift position and the tilt position are determined based on the actuator positions.

13. Method as claimed in any of the preceding claims, wherein the seating system characteristics restrictions include a maximum lift height, a minimum tilt angle, and a maximum tilt angle.

14. Method as claimed in any of the preceding claims, wherein the drive characteristics settings include a maximum driving speed and / or maximum braking force.

15. Method as claimed in claim 14, wherein step d) involves setting the maximum driving speed with a resolution of at most 10% increments, such as at most 5% increments, such as at most 1% increments, in a range of 0-100% of the rated top speed of the power wheelchair (1).

16. Method as claimed in any of the preceding claims, wherein step b) involves determining the inclination angle and the roll angle by means of an inertial measurement unit (13).

17. Power wheelchair (1) comprising: a chassis (3), a seating system (9) comprising: a lift and tilt device (9a) mounted to the chassis (3), and a seat assembly mounted to the lift and tilt device (9a); and17 a control system (15) configured to perform the method as claimed in any of the preceding claims.

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