Therapeutic Pedal Car

Designers: Amanda DeQuattro, Jamie Leong, David Houck, and Izundu Obi-onuoha

Client Coordinator: Dr. Melissa Scales

Supervising Professor: Larry Bohs

httpv://www.youtube.com/watch?v=0LaE77_jqFU

Blue Therapeutic Pedal Car

Figure 1: Therapeutic Pedal Car

INTRODUCTION

Our client is a four year old child with cerebral palsy who enjoys playing in a Little Tikes push car. However, because of his relative strength in extending compared to flexing his legs, he typically pushes himself backwards, eventually running into a wall or other obstacle.  The goal of this project is to create a car that moves forward while the client extends his legs.  Additional goals are to provide a steering mechanism the client can operate, and to improve the client’s interaction with other children on the playground.  The Therapeutic Pedal Car uses a modified Power Wheels toy car with custom left/right pedals, a control circuit, and a steering extension bar. Using the device, the client can use his legs to move forward, thereby improving his independence and fostering interaction with other children on the playground.

SUMMARY OF IMPACT

With the modified Power Wheels car, the client can drive forward and utilize his vision and modified steering wheel to avoid obstacles. Other children have been excited to see the client using the car, thereby increasing his contact and interactions.  The client’s therapist commented, “The biggest benefit of the car built for (the client) is that other children in his class now flock to him and play with him and the car when before he was a solo kiddo when he played.”

TECHNICAL DESCRIPTION

The Therapeutic Pedal Car (Figure 1) comprises a commercial Lil Ford Power Wheels car, two switch pedals, a control circuit,  an extended steering bar, a seat belt, and an emergency stop switch. Two commercial foot switch pedals (Hosense HF1) attach to a wooden panel, which is secured to the foot area of the powered car.  The pedals are oriented with the compressible side upward to provide easiest actuation by the client. If desired, the force required to push the pedals can be varied by the client’s therapist by removing the top piece of each pedal and changing to stronger springs, which have been provided.  To help keep the client’s feet in proper position for the pedals, a curved piece of high-density polyethylene is secured between the car seat and pedals, two wooden panels are attached to the outer side of each of the pedals, and an upright foam noodle is placed between the pedals.  Additional foam noodles rest on either side of the seat, keeping the client centered and secure.

The control circuit includes a PICAXE microcontroller, programmed using BASIC code.  The circuit senses when a pedal is pressed, then drives the car’s motors for three seconds.  If the opposite pedal is pressed within that time, the car continues to move; otherwise, the car stops.  This algorithm requires the client to use alternate kicking motions to drive the car continuously.  An amplifier based on a Darlington power transistor transfers the drive signal from the control circuit to the car’s motors.   The circuit is powered by the commercial car’s 12V battery, regulated to 5V for the microprocessor.

Client driving the Therapeutic Pedal Car

Figure 2: Client driving the Therapeutic Pedal Car

Because the client is not strong enough to turn the car using the commercial steering wheel, an extended steering bar, made from three pieces of 1” PVC pipe and two 120 degree connectors, attaches to the wheel.  Rubber grips on the ends provide comfort and grip for the client.

A continuous seatbelt (McMaster) secures the client in place while driving. The length is adjustable to allow for the client’s growth and use by other children.  An emergency stop switch disconnects the circuit from the Power Wheels motor. This switch is mounted to the rear of the car, so that a teacher or therapist can quickly stop the car by pushing the switch if necessary.

Figure 2 shows the client driving the Therapeutic Pedal Car. Cost of components for the device is $275.

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