Platform Motion Controller

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Platform motion controller - is an electronic microcontroller-based board which task is a smooth, fast and energy efficient control of the wheel driving and rotating motors. It is based on the ATMEL ATMega64A-16 @ 14.7456 MHz µC, however, since a single board controls a bunch of motors simultaneously (using a software emulated adaptive PID control) the solution is highly demanding on floating point computational power, which may lead to changing µC from ATMega series to ARM7 (e.g. NXP LPC2103) in the future revisions.

Position feedback angle, read by incremental rotary encoder with index/dir and zero tracks, is returned to control logic for dynamic regulation.

One of the six chassis units
File:Platform-motion-design.png
Sketch of the mobile platform components

Contents

Actuators

Geared DC motors TRW Globe IM-15 series, model 409A6024. Six units for rotation plus six units for wheel drive.

→ Motor DC short stack, 24 VDC, 5200 rpm (±10%), current @ no load = 0.14 A, rated torque = 4.0 oz*in, current at rated torque = 6.00 oz*in/amps, resistance 9.0 Ohms.
→ Gearbox (gear ratio 1:100, torque multiplier 51.0, max continuous torque 178 oz*in = 0.128 kg*m).
→ Total length = 4.189 inches = 106.4 mm.

Total power: Max contiguous torque = 178 oz*in = 1.256 N*m = 12.81 Kg*cm. See oz·in→N·m, N·m→kg·cm

Sensors

Optical interrupter VISHAY TCST1300 (0.25 mm aperture).
Current sensor - shunt resistive voltage drop estimated with ADC

All optical sensors are mounted on a PCB in a sensor placeholder where the encoding disk is also located.

Sensor Placeholder Drawing

Sensor groups

Version 5

Version 5 is planned for production. It is capable of driving six DC motors and use encoder output data to form a closed loop control. Two PMC boards are able to drive and direct wheels (12 motors total). Inter-board communication is available through the I2C interface. Board to system PC communication is performed with UART.

Schematic capture

Platform Motion Controller schematic capture (rev. 5)

PCB Layout

Two-sided PCB is shown below:

A two-sided PCB layout of the Platform Motion Controller (rev. 5)

Device photo

A photo of the complete Platform Motion Controller (rev. 5)

Parts list

Test results

Flaws

Versions 4 and below

See also


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