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WC-132 – WheelCommander™ Motion Controller

The WheelCommander™ controller takes the burden of complex feedback control firmware off of the main robot controller. It provides powerful closed-loop control of two wheeled robots using simple RS-232 or I2C interface commands.

Boe-Bot with Bluetooth interface and WC-132 controller.
Example robot: BoeBot with Bluetooth interface and WC-132 motion controller.

Applications

  • Expand the Parallax BoeBot to enable even more interesting educational activities
  • Add on to your existing Sumo robot so you can concentrate on creating a winning strategy
  • Build a complete PC-controllable mobile robot using third-party wireless serial adapters (such as Bluetooth)
  • Relieve your main robot controller of managing the wheels so you can concentrate on the fun stuff

Features

  • Closed loop velocity and rate of platform rotation
  • Closed loop position and angle of rotation
  • Four general purpose analog inputs
  • Four general purpose digital inputs or outputs
  • Power and ground pins available for each analog or digital input/output
  • Fully compatible with the WW-01 and WW-11 WheelWatcher™ encoders for servos
  • Compatible with the WW-02 and WW-12 WheelWatcher encoders using separate dual motor driver board
  • Code examples for common robot controllers
  • Example code and support DLL for wired or wireless Windows programs
  • Firmware upgradable using provided Windows configuration wizard and seperately available RS232 level converter

Description

The WC-132 WheelCommander controller is a powerful yet tiny motion control module for use with the Nubotics WheelWatcherTM encoders. Unlike the many servo controllers on the market, the WC-132 uses the Nubotics WheelWatcher encoders to close the loop. It also provides general purpose digital I/O lines and analog inputs for interfacing with your sensors.

The WheelCommander controller takes the burden of complex feedback control firmware off of the main robot controller, and so provides powerful closed-loop control using simple RS-232 or I2C interface commands.

Further, the WC-132 can be given the dimensions of the robot platform – wheel diameter and wheel base – and so can accept velocity, rotation rate, position, and angle commands in real-world units, not arbitrary encoder clicks.

There are four digital I/O pins for general purpose use, as well as four analog I/O pins. Servo and logic supply voltages can be measured and compensated for.

Compatibility

The WC-132 is fully compatible with the WW-01 and WW-11 WheelWatcher encoders and continuous rotation servos.

The WheelCommander WC-132 controller also supports the WheelWatcher WW-02 and WW-12 encoders and Solarbotics gearhead motors, or the WW-01 and WW-11 encoder with servos that have had their control electronics removed, using a third-party dual H-bridge motor driver board, or the future Nubotics WheelDriver dual motor driver board that stacks right on top of the WC-132.

NOTE: when using the WheelCommander with the WW-11 or WW-12 WheelWatcher encoders, connect them in quadrature mode rather than sign/magnitude, then select quadrature as the encoder type in the Wizard, on the Motor and Encoder Settings tab.  This is different from the WW-01 and WW-02 -- they used sign/magnitude by default, which is also the default in the Wizard.

H-bridges that use either sign-magnitude or locked-antiphase control signals are supported. Single or dual (inverted and non-inverted) direction lines are also supported, which makes the WC-132 compatible with the Solarbotics "Secret Motor Driver Kit." The PWM frequency can be adjusted between 2KHz and 64KHz.

The I2C interface requires the use of an I2C master that supports clock stretching, and supports data transfer rates up to 400Kbits per second.

  WC-132 + servos

Click photo to enlarge.

WheelCommander controller shown with WW-01 Wheel Watcher encoders and servos sold separately.

* Requires Adobe Acrobat Reader:

 

WC-132 PCB

Click photo to enlarge.

WheelCommander printed circuit board shown.


Configuration Wizard

Setting up and tuning the control loops is easy using an RS232 level converter or USB serial port converter (we recommend the Acroname USB Serial Interface Connector or the RS232 Serial Interface Connector) and WCWizard, the WheelCommander configuration wizard, which runs under Windows 2000, Windows XP, and Windows Vista. The wizard helps you perform the following:

  • set up the serial port parameters and/or I2C slave address
  • upload new firmware
  • define the robot chassis geometry (wheel diameter and spacing, forward direction)
  • configure motor connections (servo vs. H-bridge; H-bridge interface details)
  • configure encoder settings (encoder type -- quadrature or sign/magnitude; resolution in ticks per wheel revolution)
  • invoke the WheelCommander controller's built-in motor calibration routine
  • interactively tune the velocity PID parameters with a graphical velocity display
  • interactively tune the position PID parameters
  • test the robot using an interactive driving dialog

WCWizard Velocity Tuning

Screen capture of WCWizard during Velocity PID Tuning (click to enlarge)


WC-132 controller

  • Printed circuit board, preassembled
  • Two 6" four lead color-coded cables (longer cables are available; contact info at nubotics dot com)
    (note: the cables pictured are for use with the WW-01 or WW-02; the cables provided now are different, and work with the WW-11 and WW-12)
  • One 6" four lead color-coded I2C cable (not pictured)
  • Servos, wheels and WheelWatcher encoders not included

WC-132 Parts


Block Diagram

WC-132 Block Diagram
(click to enlarge)


©2004-2013 Noetic Design, Inc. All Rights Reserved. Nubotics, WheelWatcher and WheelCommander are trademarks of Noetic Design, Inc.