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Issue #200 March 2007
Inertial Rolling Robot
by Jeff Bingham & Lee Magnusson
Start | Electronics | Drive Motor | Servo Motor | Pressure Sensor | Software | DC Drive Motor Control | Servo Motor Control | Mechanical Components | Manufacturing | Assembly | Findings | Sources & PDF
ELECTRONICS
The robot employs a single driven pendulum inside of a sphere. With 2
degrees of freedom, it drives and tilts the ball (see Figure
1). With this geometry, the robot can reach high speeds, steer, and
jump. In addition, it doesn’t get stuck when it flips over. As a toy,
it exhibits enough entertaining motion to be quite endearing and very
robust. As a project, it offers an exciting venture into mechanical and
electronic design.
The robot’s electronics perform two main functions, actuation for motors and sensors for feedback. There is actuation by means of both a bidirectional brushed DC motor and a digital proportional servo motor (see Figure 2). The two motors provide motive force and turning ability, respectively.
The robot has a pressure sensor and a motor-current sensor, although the latter was not enabled in the current software design. The main processor is a Renesas Technology H8/3664 microcontroller (see Figure 3). We used a protoboard for ease of construction. The DC drive motor is powered by a 12-V battery source consisting of 10 NiMH batteries. The servomotor and the remainder of the electronics are powered by a regulated 5-V source.
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| Figure 3—The H8/3664 microcontroller interfaces with PWM output to a drive motor and a steering servomotor. There is input from a pressure sensor and a current sensor on the drive motor, which interfaces through the microcontroller’s ADC port. |
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