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Advance Micro R/C Robot Controller Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 1/9
Advance Micro R/C Robot Controller

Specifications

Four channel R/C style signaling.

Accepts pulse widths from .85 to 2.15 ms (IFI compatible)

Two calibrations options

Multi-mode Auxiliary channel:
o
Normal PWM
o
Servo mode
o
Spin Control mode
o
Fwd-off-Rev relay.

Limit switch inputs for PWM, Servo and Relay options.

Interfaces to standard OSMC power drivers

Robust signal processing for smooth, reliable fail-safe operation.

Five user programmable inputs via screwdriver adjustments

Left/Right channel mixing for single stick operation

Adjustable exponential curve for main drive channels

Flip input for invertible robots corrects drive while inverted

Tether port for operation while transmitter is impounded (or the battery is dead)
Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 2/9

User Adjustable Inputs
There are five user adjustable
inputs on the uRRC 2.0 controller.
Two apply only to the Auxiliary
channel and have alternate
functions when the Auxiliary
channel is being used as a servo.
The other three apply only to the
main drive, left and right, channels.
ACCEL
Sets the power rate of change
value. The maximum is roughly
the amount of time, in seconds, it
takes to go from 100% to 100%
power output. Note, the Auxiliary and Left/Right channels have differing maximum
amounts.
Brake
Sets the amount of braking when the output drive level is zero. Full counter-clockwise
sets 0% braking (coasting) and full clockwise sets 100% braking.
Curve
The CURVE control on the main drive modifies the R/C input signal with an exponential
curve. The exponent value can be modified from 1 (no curve) to 2.4, which is a fairly
steep curve. Below is a table graphing the various curves available. Note, even a
modest curve of 1.4 gives a soft, wide dead band.
0
50
100
150
200
250
300
0
100
200
300
Input
Output
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 3/9
Calibration
R/C signal status and Calibration controls are
above the LEFT/RIGHT controls as illustrated.

The status light winks once per good R/C signal,
per one-second cycle. If one wink, only one
good signal has been detected. If two winks,
then two good signals have been detected and
so forth.
Calibrating to your radio
1. Connect your radio (or computer), disconnect the outputs (if practical) and apply
power to the unit.
2. Restore the trim values to their center point and verify the STATUS LED winks
once for each channel that has an R/C signal connected
3. Press and hold the CALIBRATE button for one second, until the STATUS LED
blinks a steady 2 Hz.
4. Move all controls from one extreme to another. This sets the range of the
calibration.
5. Press and hold the CALBRATE button again. The STATUS LED should resume
winking, once for each channel of R/C signals.
6. If appropriate, adjust your trim settings to zero each channel and illuminate the
COAST LED.
7. If the center setting of the transmitter was off a large amount, it might be
necessary to repeat the calibration procedure a second time.
Restoring Factory Settings
The default calibration settings are suitable for most off the shelf R/C gear. The default
settings are 1.150 ms to 1.850 ms, with 1.500 ms center. Performing the calibration
procedure with no signal attached to the controller, or not varying the stick positions,
restores default settings.

1. Apply power.
2. Press the CALIBRATE button, hold until the STATUS LED flashes steadily, about
one to two seconds.
3. Press and hold the CALIBRATE button a second time until the flashing stops.
The default values will be restored. Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 4/9
Mode Switch
Various Auxiliary modes and main channel mixing are selected with the MODE switch.
Mode switches are active, or 1 when in the open, or up position.



Mode Switch location



Close up view

Mix selects normal (tank style) vs. mixed or single stick control on the Left and Right
channels.

Mode
Mix
Normal (Tank)
Down
Mixed (Single stick)
Up
Main Drive Mix Table

BEC (Battery Eliminator Circuit) optionally powers the R/C receiver from the board
power.

Mode
BEC
On
Down
Off
Up
Mode Switch BEC table

Auxiliary Channel Modes

Mode
A1
A0
Normal PWM
Down Down
Servo
Up
Down
Spin Control
Down Up
Relay
Up
Up
Auxiliary Modes Table
Normal PWM
This mode is straight R/C pulse to PWM with dead-band, variable brake and variable
acceleration support. Note: Exponential curve does not apply to the Auxiliary channel. Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 5/9

Servo Controller
The uRRC 2.0 controller supports a position feedback servo mode on the Auxiliary
channel. The Servo mode is selected with the mode switch A0 set to OFF (UP)
position.




Auxiliary Servo Connection Block

Close up view

The auxiliary servo wiring is illustrated below. The position feedback potentiometer is
oriented such that a forward command on the AUX channel will increase the voltage at
the connection labeled SERVO. Forward motion causes the potentiometers wiper to
rotate towards the +5V connection.

The High and Low limit switches are optional and are used to disable forward and
reverse commands when their respective limit switches are closed. When disabled, the
controller applies maximum brake to the motor to arrest motion.



Tuning the Servo controller
All servomechanisms need to be tuned for the particulars of the hardware involved.
With sufficient math and data the parameters can be calculated, but that is way beyond
the scope of this users guide. In practice, by tweaking two parameters good enough
performance can be achieved.
Larry Barello
©
2003
uRRC 2.0 Users Guide
pg 6/9
The two parameters are GAIN and DAMPENING. The former tells the controller how
hard to drive the motors when there is an error between the commanded position and
the actual position. The latter tells the controller how soon to start cutting the power
when approaching the set point so it doesnt overshoot and oscillate.

On the uRRC 2.0 servo controller, the Auxiliary ACCEL and BRAKE controls are used
for GAIN and DAMPENING, respectively. Use the following procedure for tuning the
controller to a particular hardware configuration.

1. With the power off, turn both the GAIN and DAMPENING controls completely
counterclockwise (zero gain and dampening).
2. With the motor mechanically disconnected, apply power to the system. Set the
control input some were in the middle of its range.
3. Rotate GAIN clockwise ¼ turn. Move the output forward to the limits and the
Yellow LED should be illuminated and the motor should be rotating in the reverse
direction. Move the output backwards to the limits and the Green LED should be
illuminated and the motor rotating in the forward direction. The crossover point
should be somewhere near where the control input is set.
4. With the power off, rotate the GAIN control completely counterclockwise (zero
gain) and connect the motor.
5. With the output near the center and the control input near the center, apply
power, and then slowly rotate the GAIN control clockwise. At some point the
motor should be driven to the control point and stop. It should be mushy at first.
Keep increasing the GAIN until the output starts to oscillate a bit. Strong
oscillations are BAD as they can destroy your electronics, the motor and the
mechanical stuff.
6. With the GAIN set just at the point of oscillations, you can start to increase the
DAMPENING to try and get rid of the oscillations. You can then adjust both
knobs upward a bit to get crisper more accurate operation. For maximum
performance you want the GAIN as high as possible with only one overshoot.
Too much gain or too much dampening will cause severe oscillations.

Note: Sometimes reducing the GAIN while keeping the DAMPENING high can improve
smoothness of the servo.

Spin Controller
Auxiliary spin control, selected with Mode Switch A1 in the OFF (UP) position, modifies
the standard