pxt-ev3/libs/chassis/chassis.ts

enum ChassisProperty {
    //% block="wheel radius (cm)"
    WheelRadius,
    //% block="base length (cm)"
    BaseLength
}

namespace chassis {
    /**
     * A differential drive robot
     */
    //% fixedInstances
    export class Chassis {
        // the motor pair
        public motors: motors.SynchedMotorPair;
        // the radius of the wheel (cm)
        public wheelRadius: number;
        // the distance between the wheels (cm)
        public baseLength: number;

        constructor() {
            this.motors = motors.largeBC;
            this.wheelRadius = 3;
            this.baseLength = 12;
        }

        /**
         * Makes a differential drive robot move with a given speed (cm/s) and rotation rate (deg/s)
         * using a unicycle model.
         * @param speed speed of the center point between motors, eg: 10
         * @param rotationSpeed rotation of the robot around the center point, eg: 30
         * @param value the amount of movement, eg: 2
         * @param unit 
         */
        //% blockId=motorDrive block="drive %chassis|at %speed|cm/s|turning %rotationSpeed|deg/s"
        //% inlineInputMode=inline
        //% weight=95 blockGap=8
        drive(speed: number, rotationSpeed: number, value: number = 0, unit: MoveUnit = MoveUnit.MilliSeconds) {
            // speed is expressed in %
            const R = this.wheelRadius; // cm
            const L = this.baseLength; // cm
            const PI = 3.14;
            const maxw = 170 / 60 * 2 * PI; // rad / s
            const maxv = maxw * R; // cm / s
            // speed is cm / s
            const v = speed; // cm / s
            const w = rotationSpeed / 360 * 2 * PI; // rad / s

            const vr = (2 * v + w * L) / (2 * R); // rad / s
            const vl = (2 * v - w * L) / (2 * R); // rad / s

            const sr = vr / maxw * 100; // % 
            const sl = vl / maxw * 100; // %

            this.motors.tank(sr, sl, value, unit)
        }

        /**
         * Sets a property of the robot
         * @param property the property to set
         * @param value  the value to set
         */
        //% blockId=chassisSetProperty block="set %chassis|%property|to %value"
        //% blockGap=8
        //% weight=10
        setProperty(property: ChassisProperty, value: number) {
            switch (property) {
                case ChassisProperty.WheelRadius:
                    this.wheelRadius = Math.max(0.1, value); break;
                case ChassisProperty.BaseLength:
                    this.baseLength = Math.max(0.1, value); break;
            }
        }

        /**
         * Sets the motors used by the chassis, default is B+C
         * @param motors 
         */
        //% blockId=chassisSetMotors block="set %chassis|motors to %motors"
        //% weight=10
        setMotors(motors: motors.SynchedMotorPair) {
            this.motors = motors;
        }
    }

    //% fixedInstance whenUsed
    export const chassis = new Chassis();
}