Motors cleanup (#192)

* refactoring

* moving chassis into separate project

* added set motors

libs/chassis/chassis.ts

@@ -0,0 +1,101 @@
+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
+         */
+        //% blockId=motorDrive block="drive %chassis|at %speed|cm/s|turning %rotationSpeed|deg/s"
+        //% inlineInputMode=inline
+        //% weight=99 blockGap=8
+        drive(speed: number, rotationSpeed: number) {
+            this.driveFor(speed, rotationSpeed, 0, MoveUnit.Degrees);
+        }
+
+        /**
+         * 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=motorDriveFor block="drive %chassis|at %speed|cm/s|turning %rotationSpeed|deg/s|for %value|%unit"
+        //% inlineInputMode=inline
+        //% weight=95 blockGap=8
+        driveFor(speed: number, rotationSpeed: number, value: number, unit: MoveUnit) {
+            // 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.tankFor(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();
+}