BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a proportional joystick constructed in accordance with the present invention;
FIG. 2 is functional block diagram of a wheelchair control system that includes the proportional joystick of FIG. 1;
FIGS. 3 and 4 are fragmentary cross section views of the proportional joystick of FIG. 1; and
FIG. 5 is an example of a power driven wheelchair having the proportional joystick of FIG. 1.
DESCRIPTION
FIG. 1 illustrates a wheelchair input device 10 that includes a proportional joystick 12 and a signal converter 22. The joystick 12 includes a housing 15 in which a gimbal 14 is movably mounted. Due to the internal configuration of the joystick, the gimbal is free to move within the housing along a hemispheric surface, such that each position of the gimbal corresponds to a unique two dimensional position. The two dimensional position coordinates for the gimbal are communicated by two potentiometers as will be described in more detail below. In addition to moving along the hemispheric surface, the gimbal can also be moved in a direction perpendicular to the hemispheric surface as indicated by the phantom lines in FIG. 1. This perpendicular actuation closes a switch located in the bottom of the housing. The switch provides a binary output for wheelchair control. Outputs of the joystick's potentiometers and the switch are connected to the signal converter 22 that converts the signals into wheelchair control signals that can be received by a wheelchair controller and used to set various wheelchair operating parameters. A connector 22 plugs into a standard port of the wheelchair controller. While a hemispheric joystick actuation surface is described herein, other surfaces such as a plane or other appropriate surface may be employed to implement the input device.
FIG. 2 is a functional block diagram of a wheelchair control system. The joystick 12 provides a proportional signal corresponding to the position of the gimbal to the signal converter 20. The signal converter 20 converts the proportional signal into a signal to be received by a wheelchair controller 30. For example the proportional signal can be a speed for each of the drive wheels that would cause the wheelchair to be moved in the direction the gimbal is pointing and at the relative speed indicated by the gimbal position. For example, taking the top center of the gimbal's hemispheric surface as the starting point, each ray that starts at this center defines a direction of travel and the farther the gimbal is away from the center along the ray, the faster the wheelchair would move in that direction. The proportional signal provides the x,y coordinates of the gimbal's position and the converter 20 maps those coordinates to the appropriate controller input signal to cause the controller to move the wheelchair accordingly.
The switch signal is also input to the converter 20, which routes it to the wheelchair controller as a binary input. The controller translates the occurrence of a switch actuation as a mode select or reset input, depending on the controller's current mode and the position of the gimbal when the switch is actuated. For example, if the wheelchair is in drive mode, actuation of the switch may cause the controller to place the wheelchair in a mode in which seating actuators may be controlled by moving the joystick. In this case, the controller then translates the subsequent proportional signals to control the actuators, rather than the drive wheels of the wheelchair.
FIGS. 3 and 4 illustrate a dual action input device 40 that underlies the gimbal. In FIG. 4 an actuating shaft 42 is shown that is connected to the gimbal so that movement of the gimbal is translated into movement of the shaft. The shaft 42 is pivotally connected to a first cross member 45. The cross member 45 is able to pivot within a switch support structure 60 in a direction into and out of the drawing sheet. One end of the cross member 45 is pressed into a rotatable disc 49. The disc is part of a potentiometer that outputs a voltage that is proportional to the degree of rotation of the first cross member. The shaft 42 protrudes through a second cross member 43 (FIG. 3) that is an arced, slotted, guide. Like the first cross member, the second cross member is pressed into a rotatable disc 48 that is part of a potentiometer that outputs a voltage that is proportional to the degree of rotation of the second cross member. Movement of the shaft perpendicular to the second cross member causes the second cross member and the disc to rotate and change the signal being output by the potentiometer. By pivoting within the first cross member as guided by the slot in the pivoting arced second cross member, the gimbal can be guided to all positions within the hemisphere of actuation.
A micro switch 51 is mounted within the base of the joystick on the support structure 60. The micro switch, which is normally open, can be closed by movement of the gimbal in a direction perpendicular to the hemispheric surface until the shaft contacts the switch and closes it. A biasing spring 62 is placed between the shaft 42 and the micro switch to urge the shaft out of engagement with the switch. The characteristics of the spring can be varied to provide a very light actuation force, which can be helpful to users with limited strength or control. In fact, a light action spring can make it possible for a user to actuate the switch using a single finger or a lip. Users with this type of limited mobility often could not actuate a separate reset button.
FIG. 5 illustrates a power driven wheelchair 70 that includes drive wheels 72 that are driven within hub motors 76. The proportional joystick 12 is used to control the wheelchair. Modifications can be made to the wheelchair to place the joystick within reach of the user's finger or lip. Signals from the joystick are used to provide drive signals to the hub motors and other actuators and components on the wheelchair.
While the invention is described herein in conjunction with one or more exemplary embodiments, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, exemplary embodiments in the preceding description are intended to be illustrative, rather than limiting, of the spirit and scope of the invention. More specifically, it is intended that the invention embrace all alternatives, modifications, and variations of the exemplary embodiments described herein that fall within the spirit and scope of the appended claims or the equivalents thereof.
Patent Application
20080088110
