Dynamically Simulated Characters in Virtual Environments


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    Hardware


    The photos below illustrate some of the physical components of the bike platform hardware. The bike platform was designed and constructed by Ben Brown. In this image it is pitched forward the maximum amount. The platform is balanced such that when it is not actively controlled, it moves to a level pitch.

    [Bike Platform]

    The bike is supported upon the wooden platform by a CompuTrainer stand. We also use the load generator provided by CompuTrainer. There is a serial connection between an SGI Indy and a Motorola 68332 microcontroller. The 68332 controls the load generator to increase the difficulty of pedaling. You might be able to detect from the image that we replaced the blue freewheel that CompuTrainer attached to the load controller with a bigger wheel.

    [Bike Stand]

    The front wheel of the bicycle sits in a medal trough that rotates about a point in line with the bicycle's headset. An optical encoder measures the amount of rotation of the front wheel between +/- 20 degrees. The optical encoder is connected to the 68332, which uses a serial connection to communicate with the SGI Indy.

    [Bike Front Wheel Encoder]

    The pitch of the bike platform is actively controlled by a motor positioned in the center the platform. The motor provides transport through the full range of motion in about 2 seconds. The output of the motor is controlled by the Motorola 68332.

    [Motor Below Bike Platform]

    The final piece of the system is a Motorola 68332. We use this hardware to read three analog ins, and to write two analog outs. The hardware performs analog to digital pulse-width modulation and digital to analog pulse-width modulation.

    [332 Controller]