Single and Two-motor driver objects P2 Spin2/Pasm2 for our 6.5" Hub Motors with Universal Motor Driver Board
Last Udpated: 220215 15:44 MST
As I'm researching I'm studying both LEGO Mindstorms motor control since this is for 9-14 year olds to program and I'm studying BlocklyProp, the Parallax Offering. I'm intending to develop either side by side interchangable control methods or some sort of blend of the different methods. Let's see how it turns out! For now I'm recording initial thoughts here and it will all gradually be whittled down to the target interface specs for the steering and motor objects.
My thinking so far is that the motor control system is a live system. We as programmers simply adjust the control values and can read the current state/historical status values from the system. This form of thinking allows us to use code that monitors the motors and other sensors and sends values to the drive system -OR- with very little effort use serial receiver code which listens to a multi-variable controller like our Futaba RC controller and forwards value changes to the drive system.
The steering API makes it easy to make your robot drive forward, backward, turn, or stop. You can adjust the steering to make your robot go straight, drive in arcs, or make tight turns. The steering object is for robot vehicles that have two motors, with one motor driving the left side of the vehicle and the other the right side.
The steering API controls both motors at the same time, to drive your vehicle in the direction that you choose. Steering-direction is used to re-interpet the power value that is actually sent to each wheel.
The steering API also provides an alternative form of control where you can make the two motors go at different speeds or in different directions to make your robot turn.
| LEGO Drive-like Interface | Description |
|---|---|
| >--- CONTROL | |
PUB driveBothDuration(power, direction, bBrakeAtEnd, seconds) |
Turns both motors on for the number of {seconds}, then turns them off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {power} and {direction} inputs. |
PUB driveBothDegrees(power, direction, bBrakeAtEnd, degrees) |
Turns both motors on, waits until one of them has turned for the number of degrees of rotation {degrees}, then turns both motors off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {power} and {direction} inputs. This can be used to make your robot travel a specific distance or turn a specific amount. 360 degrees of rotation corresponds to one full turn of a motor. |
PUB driveBothRotations(power, direction, bBrakeAtEnd, rotations) |
Turns both motors on, waits until one of them has turned for the number of {rotations}, then turns both motors off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {power} and {direction} inputs. This can be used to make your robot travel a specific distance or turn a specific amount. |
PUB driveEachDuration(leftPower, rightPower, bBrakeAtEnd, seconds) |
Turns both motors on for the number of {seconds}, then turns them off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {leftPower} and {rightPower} inputs. |
PUB driveEachDegrees(leftPower, rightPower, bBrakeAtEnd, degrees) |
Turns both motors on, waits until one of them has turned for the number of degrees of rotation {degrees}, and then turns both motors off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {leftPower} and {rightPower} inputs. This can be used to make your robot travel a specific distance or turn a specific amount. 360 degrees of rotation corresponds to one full turn of a motor. |
PUB driveEachRotations(leftPower, rightPower, bBrakeAtEnd, rotations) |
Turns both motors on, waits until one of them has turned for the number of {rotations}, then turns both motors off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of your robot using the {leftPower} and {rightPower} inputs. This can be used to make your robot travel a specific distance or turn a specific amount. |
| PUB stop() | stops both motors, killing any motion that was still in progress |
| >--- CONFIG | |
| PUB resetTracking() | Resets the position tracking values returned by getDegrees()/getRotations() |
| >--- STATUS | |
| PUB getDegrees() | Returns accumulated degrees since last reset for each of the motors |
| PUB getRotations() | Returns decimal number degrees/360 as count of rotations since last reset for each of the motors |
| PUB getStatus() | Returns: moving to position, holding position or off |
NOTE1 {*power} is [(-100) - 100] where neg. values drive backwards, pos. values forward, 0 is hold
NOTE2 {direction} is [(-100) - 100] A value of 0 (zero) will make your robot drive straight. A positive number (greater than zero) will make the robot turn to the right, and a negative number will make the robot turn to the left. The farther the steering value is from zero, the tighter the turn will be.
NOTE3 {bBrakeAtEnd} is T/F where T means the motor is stopped and is held in position and F means motor power turned off and the motor is allowed to coast
| BlocklyProp-like Interface | Description |
|---|---|
| >--- CONTROL | |
PUB setDriveDistance(ltDistance, rtDistance, units) |
where {*distance} is in {units} [ticks, in., or mm] |
| PUB setDriveSpeed(ltSpeed, rtSpeed) | where {*speed} is [(-128) - 128] and zero stops the motor |
| PUB stop() | stops both motors |
| >--- CONFIG | |
| PUB setAcceleration(rate) | where {rate} is [100 - 2000] ticks/s squared (default is 400 ticks/s squared) |
| PUB setMaxSpeed(speed) | where {speed} is [0 - 128] ticks/s (default is 128 ticks/s) |
| PUB setMaxSpeedForDistance(speed) | where {speed} is [0 - 128] ticks/s (default is 600? ticks/s) |
| PUB calibrate() | (we may need this?) |
| PUB resetDistance() | Resets the distance tracking values |
| >--- STATUS | |
| PUB getDistance(units) | Returns the distance in {units} [ticks, in., or mm] travelled by each motor since last reset |
NOTE "ticks" in BlocklyProp: are single encoder ticks, which are 3.25 mm long and are used as (ticks|in|mm) distance values.
SUGGESTION: Let's rethink the use of ticks (not applicable to our BLDC motor.) Let's use a unit of measure that makes sense.
DOC ISSUE?: Default of 600 ticks/s setMaxSpeedForDistance(speed) can't be set. Does this mean the docs are incorrect?
The reference material studied and from which the above information was extracted is found at: Robot API docs
With the Motor Control API you can turn a motor on or off, control its power level, or turn the motor on for a specified amount of time or rotation and retrieve its status.
LEGO Mindstorms provides control over large, medium and small motors using the following API:
| LEGO Motor-like Interface | Notes |
|---|---|
| >--- CONTROL | |
PUB moveDuration(power, bBrakeAtEnd, seconds) |
Turns the motor on for the number of {seconds}, then turns it off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of the motor using the {power}. |
PUB moveDegrees(power, bBrakeAtEnd, degrees) |
Turns the motor on for the number of degrees of rotation in {degrees}, then turns it off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of the motor using the {power}. 360 degrees of rotation results in one full turn of the motor. |
PUB moveRotations(power, bBrakeAtEnd, rotations) |
Turns the motor on for the number of {rotations}, then turns it off (or holds) based on {bBrakeAtEnd}. Control the speed and direction of the motor using the {power}. 1 rotation (or 360 degrees) results in one full turn of the motor. |
| PUB disable() | Turns off active motor control |
| >--- CONFIG | |
| PUB resetTracking() | Resets the position tracking values returned by getDegrees()/getRotations() |
| >--- STATUS | |
| PUB getDegrees() | Returns accumulated degrees since last reset |
| PUB getRotations() | Returns decimal number degrees/360 as count of rotations since last reset |
| PUB getPower() | Returns the current motor power level if the motor is running (1-100), or 0 if the motor is stopped |
| PUB getStatus() | Returns: moving to position, holding position or off |
NOTE1 {power} is [(-100) - 100] where neg is drive backwards, pos is forward, 0 is hold
NOTE2 {bBrakeAtEnd} is T/F where T means the motor is stopped and is held in position and F means motor power turned off and the motor is allowed to coast
BlocklyProp provides control of a Feedback 360° Servo. Control for these servos offers Velocity Control and Angular Control subsystems.
| Fb360 Servo-like Interface | Description |
|---|---|
| >--- CONTROL | |
| PUB setSpeed(degrPerSec) | Where +/- degrees/Sec rotation rate (capped by limitSpeed()) |
| PUB gotoAngle(degrees) | Where +/- degrees (relative to home as last set) |
| PUB moveAngle(degrees) | Where +/- degrees (relative to curr position) |
| PUB disable() | Turns off active motor control |
| >--- CONFIG | |
| PUB limitAccel(value) | Where value (°/s^2) [600 - 7200] determines how quickly the servo will transition to a new speed setting, in units of degrees per second squared |
| PUB limitSpeed(value) | Where value (°/s) [1 - 1080] determines the maximum rotation speed in units of degrees per second, independent of direction |
PUB adjustVelocityControl(kP,kL,kD,I) |
(Speed) Defaults: kP=500,kI=0,kD=0 and I=0 |
PUB adjustAngularControl(kP,kL,kD,I) |
(Position) Defaults: kP=12000,kI=600,kD=6000 and I=1000 |
| PUB resetTracking() | Reset motor position tracking |
| PUB setHome() | Tells motor that current position should be thought of as home |
| >--- STATUS | |
| PUB getTurnCount() | Returns +/- count of revolutions since last reset |
| PUB getPosition() | [0-359] Return the current postion of the motor where 0 is home position as last set |
| PUB getStatus() | Returns: moving to position, holding position or off |
| PUB getSpeed() | Returns +/- degrees/Sec rotation rate, 0 if stopped |
BlocklyProp also provides control for a Continuous Rotation (CR) Servo.
| CR Servo-like Interface | Description |
|---|---|
| >--- CONTROL | |
| PUB setSpeed(speed) | Where speed is [(-200) - 200], neg values backward, pos forward, 0 is stop |
| PUB setRamp(ramp) | Where ramp [0 - 100] is amount of change ea. 20ms cycle |
| PUB disable() | Turns off active motor control |
| >--- STATUS | |
| PUB getSpeed() | Returns speed [(-200) - 200], neg values backward, pos forward, 0 stopped |
| PUB getRamp() | Returns ramp [0 - 100] the requested amount of change ea. 20ms cycle |
| PUB getStatus() | Returns: moving, holding position or off |
The reference material studied and from which the above information was extracted is found at: Feedback 360° and CR Servo API docs
If you like my work and/or this has helped you in some way then feel free to help me out for a couple of ☕'s or 🍕 slices!
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