WO1994017964A1

WO1994017964A1 - Robotic arm for wheelchair

Info

Publication number: WO1994017964A1
Application number: PCT/US1994/001437
Authority: WO
Inventors: Christopher B. Cobb
Original assignee: Kinetic Rehabilitation Instruments, Inc.
Priority date: 1993-02-09
Filing date: 1994-02-09
Publication date: 1994-08-18
Also published as: AU6155094A; CA2155748A1

Abstract

Disclosed is a robotic arm (10) which is removably mounted to a wheelchair (12) preferably at least along one side of the wheelchair (12). Movement of the arm (10) is controlled by a joystick, although it can be controlled by any of the other control systems commonly used by disabled people. The arm (10) components (22) move in substantially the same fashion as a human arm. The joystick is used to activate four motors (30, 34, 36, 42) which control movement of the arm (10) in four different directions.

Description

ROBOTIC ARM FOR WHEELCHAIR

Background of the Invention

The present invention relates to a robotic arm and mor particularly to a robotic arm attached to a wheelchair and controlled by the occupant of the wheelchair.

Physically disabled people who are confined to a wheelchair often are not able to perform routine tasks such as answering a telephone or taking food out of a refrigerator because such objects often cannot be reached b a person sitting in the wheelchair. In addition, many people confined to wheelchairs do not have full use of thei arms, and therefore they cannot reach for objects. Other people confined to a wheelchair that have full use of their arms still cannot reach many objects because they cannot stand up or because the wheelchair prevents the person from getting close enough to an object to reach for it.

It is therefore a principal object of the present invention to provide a robotic arm which is attachable to a wheelchair.

It is a further object of the present invention to provide a robotic arm which is attached to a wheelchair and which is capable of making substantially the same motions a a human arm.

Summary of the Invention The robotic arm of the present invention is removably mounted to a wheelchair preferably at least along one side of the wheelchair. Movement of the arm is controlled by a joystick, although it can be controlled by any of the other control systems commonly used by disabled people. The arm includes a shoulder, bicep, elbow, forearm and gripping components which move in substantially the same fashion as human arm. The joystick is used to activate four motors which control movement of the arm in four different directions.

These and other features and objects of the present invention will be more fully understood from the following detailed description which should be read in light of the accompanying drawings in which corresponding reference numerals refer to corresponding parts throughout the several views .

Brief Description of the Drawings

Fig. 1 is a side elevational view of a wheelchair to which the robotic arm of the present invention is attached;

Figs. 2 (a) -2(e) are side elevational views of the robotic arm and wheelchair shown in Fig. 1 in various positions;

Figs. 3 (a) -3(f) are top plan views of the wheelchair shown in Fig. 1 which show six different positions to which the robotic arm shown in Fig. 1 can be moved;

Fig. 4 is a sectional view of the robotic arm shown in Fig. 1 which shows the four motors used in the robotic arm;

Fig. 5 is a view of the robotic arm shown in Fig. 1 which shows the various directions of movement of the arm;

Figs. 6(a) and 6(b) are side and front views of the mounting brackets for the shoulder motor of the robotic arm shown in Fig. 1;

Fig. 7 is a top plan view of the joystick control utilized in a preferred embodiment of the invention;

Fig. 8 is a detailed view, partly in section, showing the operation of the gripping hand of the robotic arm of Fig. 1;

Fig. 9 is a sectional view of the attachment mechanism attaching the arm shown in Fig. 1 to a wheelchair;

Fig. 10 is a electronic schematic diagram of the circuitry for controlling the motors of the robotic arm of the present invention. Detailed Description of the Preferred Embodiments Referring to Fig. 1, the robotic arm 10 of the present invention is attached to a wheelchair 12. The arm 10 is attached at a shoulder joint 14 located in a shoulder housing to which a bicep section 16 is attached. .An elbow 18 is attached between the bicep 16 and a forearm section 19. A gripper base 20 and a gripper 22 are attache to the forearm 19. These components will be described belo in greater detail.

Turning now to Figs. 2 (a) -2(e), the robotic arm 10 is shown in various positions. In Fig. 2(a) the arm 10 is shown in its storage or at rest position where it is completely retracted and out of the way of the wheelchair occupant. The arm 10 preferably folds between the wheel 23 and the seat of the chair 12 so that the occupant can still rotate the wheels to move the wheelchair. Fig. 2(b), shows the position of initial actuation where the arm 10 begins to rise in a way in which the forearm 19 remains substantially parallel to the armrest 24 of the wheelchair 12. This movement is primarily initiated by the motor 30 controlling the shoulder (see Fig. 4) . In Fig. 2(c), the arm 10 begins its forward motion which is under the control of both a shoulder motor 30 and an elbow motor 36 and it remains substantially parallel with the top armrest. In Fig. 2(d), the arm 10 is shown extended from the wheelchair 12 with such motion being controlled by both the shoulder and elbow motors 30, 36. Finally, Fig. 2(e) shows the arm 10 substantially fully extended in a forward position.

Referring to Figs. 3 (a) -3(f), additional movement positions of the arm 10 are shown. Fig. 3(a) corresponds to the position of the arm shown in Fig. 2(a) in which the arm 10 is at rest in the inactive position, tucked away yet remaining in the site of the wheelchair occupant. Fig. 2(b) shows the arm 10 being extended towards its ultimate destination. This position of the arm 10 corresponds to the position of the arm 10 shown in Fig. 2(d) . In Fig. 3(c), the arm 10 is fully extended in a fashion similar to that shown in Fig. 2(e) . In Fig. 3(d), the arm 10 is shown rotating about the elbow joint 18 and in Fig. 3(e) the forearm section 19 is brought inwardly towards the controller's chest through action of the elbow motor 36. Finally, the forearm section 19 of the arm 10 is rotated towards the wheelchair occupant's mouth or face area which will be convenient to enable the wheelchair occupant to bring food or other objects to his/her mouth or enable him/ her to bring a phone to his/her ear, etc.

Referring to Fig. 4, the four motors for the arm 10 of the present invention are shown. The shoulder motor 30, which preferably moves at a velocity of 2 rpm, is mounted to the wheelchair under the seat (or behind the seat) and is connected to a shoulder joint housing 32. The wrist motor 34, which also rotates at 2 rpm, is mounted within the shoulder joint housing 32. The bicep 19 is slightly recessed into the shoulder joint housing 32 (to provide additional stability) and slides over the output shaft 33 of the wrist motor 34.

An elbow motor 36, which causes a rate of change of 90 degrees per 7 seconds, is mounted in the hollow of the bicep. The elbow 18 is a typical worm drive set up so that the end of the output shaft 40 of the motor 36 is the drive shaft of the worm gear. A gripper motor 42, which causes a 3 inch closure in 5 seconds, is inserted into the forearm 19 to control movement of the manipulator 22. Stabilizers 44, which are preferably thermoplastic with a steel bushing in the center, are placed about the shaft 46 of the gripper motor 42 so as to prevent the shaft from wearing out quickly. The shaft 46 has a threaded end onto which the gripper is secured in a manner which will be described in greater detail below. The wiring passes through the arm which is hollow, and grommets may be used to house the wires around motors.

As shown in Fig. 5, the arm 10 will move about three different axis of rotation and the gripper fingers will move toward and away from each other. Movement in the directions of arrows 52 for 135 degrees of motion is controlled by the shoulder motor 30, and movement in the direction of arrows 54 for 180 degrees of motion is controlled by the wrist motor 34. The elbow motor 36 controls movement of the arm in a direction of arrows 56 for 135 degrees of motion and the gripper motor 42 controls the clamping and unclamping of the gripper fingers in the direction of arrows 58. All of the motors utilized in the present invention are stepper motors which will enable the arm to maintain selected positions, and the lifting capacity of the arm should be approximately 8 pounds.

Referring to Figs. 6(a) and 6(b) the bracing of the shoulder motor 30 is shown in detail. Since this motor must be securely mounted, it is important that it is supported on as many sides as possible. Brackets 62 support the motor from above, while brackets 64 support the motor from below. In a preferred embodiment there are four brackets above the motor 30 and four brackets below the motor 30, each being secured to the frame of the wheelchair 12. It may be necessary in some applications because of torque requirements to utilize a brace 66 to further strengthen the brackets holding the motor to the wheelchair.

Referring to Fig. 7, the various positions of the joystick are shown. The normal forward, reverse, right and left indicators are at right angles to each other. Between the forward and left positions, position 70 is used to indicate the position required to move the arm 10 inwardly towards the occupant of the wheelchair, and position 72 between the forward position and the right positions, identifies location to which the joystick 68 must be moved in order to move the arm 10 out away from the wheelchair 12. Positions 74 and 76 identify the "unclamp" and "clamp" positions which control the movement of the fingers of the gripper 22.

The gripper 22 is shown in greater detail in Fig. 8. The gripper includes fingers 80, which extend from the gripper housing 82 in a direction which is away from the opposite finger and after a few inches then heads in a direction towards the opposite finger. The fingers finally meet at a flat surface at their ends 84. Round or irregularly shaped items can be gripped between the fingers and small items such as paper that need to be securely gripped can be gripped by surfaces 85 of the finger 80. As the gripper motor 42 rotates the gripper shaft 46, which includes a shredded end 86, the central mounting member 88 is moved either toward or away from the gripper fingers 80 depending upon a direction of rotation. As the mounting member 88 is pushed upwardly in the housing toward the fingers 80, the fingers 80 begin to separate and when the mounting member 88 is moved towards the gripper motor 42, the fingers come together. Springs 90 are connected to each finger 80 so that the fingers 80 will lock together when in a closed position.

Referring to Fig. 9, the shoulder joint housing 32 is mounted over the shaft 31 of the shoulder motor 30. The shoulder motor shaft 31 has notches 35 which are locked by ball plungers 37 to secure the shoulder joint housing 32 to the shoulder motor shaft 31. The ball plungers 37 are utilized because they will release upon application of an excess force that is inflicted to the arm to enable the arm to release from the shoulder and thereby avoid being damaged. Electrical connections made between male connectors 39 and female connectors 41.

Turning now to Fig. 10, the electrical connections for the joystick and motors are shown. Relay Rl is connected to the "forward" position of the joystick and causes the shoulder to move in a forward direction and relay Rl' is connected to the "reverse" position of the joystick which activates shoulder motor 30 to reverse the direction of movement of the shoulder. Relay R2 is connected to the "left" position of the joystick and relay R2 ' is connected to the "right" position of the joystick and these two relays control the movement of direction of the wrist which is controlled by wrist motor 34. Relay R3 is connected to the "in" location of the joystick and relay R3 ' is connected to the "out" version of the joystick, and these relays R3 and R3 ' activate the elbow motor 36. Finally, relay R4 and relay R4' are activated by the "clamp" and "unclamp" positions of the joystick which are controlled by gripper motor 42.

A twelve volt battery 94 which is generally used to control a wheelchair is utilized to provide power to the arm 10. A 10 amp fuse 96 is used to prevent electrical overloads, and a transformer 98 transforms the battery voltage to 3 volts DC which is a voltage that is low enough to avoid any injury to the operator of the wheelchair should there be a malfunction.

While the foregoing invention has been described with reference to the preferred embodiments, various alterations and modifications will occur to those skilled in the art. For example, an arm 10 could be mounted to each side of a wheelchair or to the side of a hospital bed. All such alterations and modifications are intended to fall within the scope of the appended claims.

Claims

What is claimed is:

1. A robotic arm comprising a motor driven, rotatable arm; means for connecting said arm to a frame of a wheelchair; means for manipulating objects, said means for manipulating being connected to said arm at an end of said arm opposite an end of said arm connected to said frame of said wheelchair; means connected to said arm for controlling the movement of said arm.

2. The robotic arm of claim 1 wherein said arm comprises: a forearm section connected at one end to said means for manipulating and at another end to an elbow joint connected to said forearm section; a bicep section connected at one end to said elbow joint and at another end to a shoulder joint.

3. The robotic arm of claim 2 further comprising a shoulder motor for rotating said arm around said shoulder joint in a plane substantially parallel to a rear wheel of a wheelchair.

4. The robotic arm of claim 2 further comprising a wrist motor mounted in a shoulder housing for said shoulder joint, said wrist motor rotating said bicep section about a longitudinal axis of said bicep section.

5. The robotic arm of claim 2 further comprising an elbow motor mounted in said bicep section, said elbow motor controlling rotation of said forearm section about said elbow joint relative to said bicep section.

6. The robotic arm of claim 2 further comprising a gripper motor mounted in said forearm section, said gripper motor controlling opening and closing of said means for manipulating.

7. The robotic arm of claim 1 wherein said means for manipulating comprises a pair of gripper fingers which are moveable toward and away from each other.

8. The robotic arm of claim 6 wherein said means for manipulating comprises a pair of gripper fingers attached to linkages housed on a base connected to said forearm section, said linkages being threadably attached to a shaft of said gripper motor.

9. A wheelchair comprising: at least four wheels connected to a frame; a seat mounted on said frame; a motor driven, rotatable arm mounted on the frame of said wheelchair; means for manipulating objects, said means for manipulating being connected to said arm and at an end of said arm opposite at an end of said arm connected to said frame of said wheelchair; means connected to said arm for controlling movement of said arm.