The Ride: A scale mock up of an amusement park ride.

Some people like to collect train sets and build elaborate sets through which they chug along. Others apparently do the same thing but with models of amusement parks and circuses.

I don't do either. I do robots, but when I was asked for some help with the motor control routines on an amusement park ride model it sounded kind of fun, so I did it.

This page shows the mock up that I built using foam core board, some hot melt glue, and a fair amount of clear cellophane tape.

 

 

The ride is essentially a 3 axis robot arm: 1) The LIFT arm, 2) the ROTATE arm, and 3) the SPINing cage. The LIFT and ROTATE arms are jointed to Hitec HS-322D Deluxe servo motors. The SPIN cage is mounted on a Hitec HS-50 micro servo. The brains of the system is a Motorola MC68HC908GP32 microcontroller board that I designed (see my HC08 board). That and a smaller board with an RS-232 interface and the HC08's MON08 circuitry is mounted in a black plastic project box.

All three motors are modified for continuous rotation. There are limit switches mounted to sense the LIFT's UP and DOWN limits of motion, and also to sense the ROTATE's limits of motion. The limit switches serve both to keep the motors from over-rotating and damaging the assembly and also to give me points of reference. On power up the ride checks the position of the LIFT and ROTATE arms and if they are not in the startup "loading" position, they move to get to that position.

The switches are actuated by a right angled piece of foamboard that is hot glued on to the arm. The photo at left shows the DOWN limit switch about to be actuated. The photo at right shows all of the switches. They are small 2 push actuator switches. If either of the two are pushed it closes the switch. The switches are connected to external interrupt inputs on the micro to ensure fast response to a limit condition.

Video clips:

Longer - windows media format, shows more angles, switches being acutated, etc

Short - windows media format 3.7 Megs, pretty quick shows basic motion

Short .mov format - same as short above but grainier and in the quicktime format

Schematic - .pdf format. I have drawn a very hi level schematic. I don't show all the support circuitry as I used my HC08 BotBoard and I didn't want to reproduce that schematic. This one should be sufficient to understand the design. The design really is just 4 switches as inputs and 3 servo outputs.

Source code - There are two C files. Ride_rev2 is the main program. Vectors08.c has the interrupt vector definition and is required for the Imagecraft C compiler which I used.