PWMMotorControl

Arduino library to control brushed DC motors by PWM.
It uses optional attached encoders to drive fixed distances.

               

Available as Arduino library "PWMMotorControl".
Contains the RobotCarBlueDisplay example.

       

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Features

• The PWMDcMotor.cpp controls brushed DC motors by PWM using standard full bridge IC's like L298, SparkFun Motor Driver - Dual TB6612FNG, or Adafruit_MotorShield (using PCA9685 -> 2 x TB6612).
• The EncoderMotor.cpp.cpp controls a DC motor with attached encoder disc and slot-type photo interrupters to enable driving a specified distance.
• The CarPWMMotorControl.cpp controls 2 motors simultaneously like it is required for most Robot Cars.
• To compensate for different motor characteristics, each motor can have a positive compensation value, which is subtracted from the requested speed PWM if you use the setSpeedPWMCompensation() functions. For car control, only compensation of one motor is required.

The motor is mainly controlled by 2 dimensions:

1. Direction / motor driver control. Can be FORWARD, BACKWARD, BRAKE (motor connections are shortened) or RELEASE (motor connections are high impedance).
2. SpeedPWM which is ignored for BRAKE or RELEASE. Some functions allow a signed speedPWM parameter, which includes the direction as sign (positive -> FORWARD).

API

Basic commands are:

• init(uint8_t aForwardPin, uint8_t aBackwardPin, uint8_t aPWMPin).
• setDirection(uint8_t aMotorDirection).
• setSpeedPWM(uint8_t aSpeedPWM).
• setSpeedPWMAndDirection(uint8_t aRequestedSpeedPWM, uint8_t aRequestedDirection).
• setSpeedPWMAndDirection(int SignedRequestedSpeedPWM).
• stop() or setSpeedPWMAndDirection(0).
• startRampUp(uint8_t aRequestedDirection).
• getSpeed(), getAverageSpeed(), getDistanceMillimeter() and getBrakingDistanceMillimeter() for encoder motors or MPU6050 IMU equipped cars.

Functions to go a specified distance:

Driving speed PWM (2.0 V) is the PWM value to use for driving a fixed distance. If it is set higher than RAMP_VALUE_OFFSET_SPEED_PWM (2.3 V), the software generates a ramp up from RAMP_VALUE_OFFSET_SPEED_PWM to requested driving speed PWM at the start of the movement and a ramp down to stop.

• goDistanceMillimeter(uint8_t aRequestedSpeedPWM, unsigned int aRequestedDistanceMillimeter, uint8_t aRequestedDirection);
  For non encoder motors, distance and drive speed PWM is used in a formula to convert millimeters into motor driving time.
• updateMotor() - call this in your loop if you use the start* functions e.g. startGoDistanceMillimeter(int aRequestedDistanceMillimeter).

Functions for cars controlling 2 motors / motor sets from CarPWMMotorControl.hpp.

• rotate(int aRotationDegrees, turn_direction_t aTurnDirection, bool aUseSlowSpeed, void (*aLoopCallback)(void)).
• Plus all functions from above like setSpeedPWM() etc. They now affect both motors.

Pictures

4WD car with IR receiver and Bluetooth module and 4 AA rechargeable batteries.	Instructable

Full bridges

This library was tested with the bipolar full bridge IC L298 and the (recommended) MOSFET full bridge IC TB6612.

The L298 has a loss of around 2 volt, which is the reason for the attached heat sink	The TB6612 has almost no loss
L298 voltages at both motor pins @7.5 V	TB6612 effective motor voltage @7.6 V

PWM period

• PWM period is 600 µs (1.6 kHz) for Adafruit Motor Shield V2 using PCA9685.
• PWM period is 1030 µs (970 Hz) for AnalogWrite on pin 5 + 6.

Examples for this library

The examples are available at File > Examples > Examples from Custom Libraries / PWMMotorControl.

Start

One motor starts with DriveSpeedPWM / 2 for one second, then runs 1 second with DriveSpeedPWM. After stopping the motor, it tries to run for one full rotation (resulting in a 90 degree turn for a 2WD car). Then the other motor runs the same cycle. For the next loop, the direction is switched to backwards.

Square

4 times drive 40 cm and 90 degree left turn. After the square, the car is turned by 180 degree and the direction is switched to backwards. Then the square starts again.

PrintMotorDiagram

This example prints PWM, speed and distance / encoder-count diagram of an encoder motor. The encoder increment is inverted at falling PWM slope to show the quadratic kind of encoder graph. Timebase is 20 ms per plotted value.

Diagram for free running motor controlled by an MosFet bridge supplied by 7.0 volt	Diagram for free running motor controlled by an L298 bridge supplied by 7.6 volt
Here you see that the speed is proportional to the PWM, but the minimal power to start the motor is 33/255 = 13% PWM or 0.9 volt.	Due to losses and other effects in the L298, the start voltage is much higher.
MosFet bridge supplied by only 3.5 volt	Start diagram for L298 with 6.2 volt
Here, the start voltage can be observed better. There is no stop at the same voltage, so the distance gets virtually negative.	Higher start voltage and a non linear speed / PWM ratio here.

TestMotorWithIMU

Prints PWM, speed and distance diagram of the right (encoder) motor of a car equipped with a MPU6050 IMU. Encoder and IMU (MPU6050) data are printed simultaneously, to compare and to detect slipping.
It does a start and stop car first with and second without ramp. It starts with DEFAULT_DRIVE_SPEED_PWM and doubles speed for next turn until MAX_SPEED_PWM.

Diagram for car controlled by an MosFet bridge	Diagram for car controlled by an L298 bridge

RobotCarBasic

Template for your RobotCar control. Currently implemented is: Drive until distance too low, then stop, go backwards and turn random amount.

BasicIRControl

Implements basic car control by an IR remote. Mapping between keys of any IR remote sending NEC protocol (all the cheap china ones) and car commands can be done in IRCommandMapping.h.
To support mapping, the received IR code is printed at the serial output if INFO is defined.

SmartCarFollowerSimple

The car tries to hold a distance between 30 and 40 cm to an obstacle. Only forward and back movement, no turn! The measured distance range is converted to a pitch as an acoustic feedback.

SmartCarFollower

The car tries to hold a distance between 30 and 40 cm to an target. If the target vanishes, the distance sensor scans to get the vanished (or a new) target.

RobotCarBlueDisplay

Requires also the Arduino library BlueDisplay.

Enables autonomous driving of a 2 or 4 wheel car with an Arduino.
To avoid obstacles a HC-SR04 Ultrasonic sensor mounted on a SG90 Servo continuously scans the environment. Manual control is implemented by a GUI using a Bluetooth HC-05 Module and the BlueDisplay library.

Compile options / macros for this library

To customize the library to different requirements, there are some compile options / macros available.
These macros must be defined in your program before the line #include <CarPWMMotorControl.hpp>, #include <EncoderMotor.hpp> or #include <PWMDcMotor.hpp>to take effect.
Modify them by enabling / disabling them, or change the values if applicable.

Name	Default value	Description
USE_ENCODER_MOTOR_CONTROL	disabled	Use slot-type photo interrupter and an attached encoder disc to enable motor distance and speed sensing for closed loop control.
USE_MPU6050_IMU	disabled	Use GY-521 MPU6050 breakout board connected by I2C for support of precise turning and speed / distance calibration. Connectors point to the rear. Requires up to 2850 bytes program memory if USE_SOFT_I2C_MASTER defined and 3756 bytes if USE_SOFT_I2C_MASTER is not defined.
USE_ACCELERATOR_Y_FOR_SPEED	disabled	The y axis of the GY-521 MPU6050 breakout board points forward / backward, i.e. connectors are at the left / right side.
USE_NEGATIVE_ACCELERATION_FOR_SPEED	disabled	The speed axis of the GY-521 MPU6050 breakout board points backward, i.e. connectors are at the front or right side.
USE_ADAFRUIT_MOTOR_SHIELD	disabled	Use Adafruit Motor Shield v2 connected by I2C instead of simple TB6612 or L298 breakout board. This requires only 2 I2C/TWI pins in contrast to the 6 pins used for the full bridge. For full bridge, the millis() timer0 is used for analogWrite since we use pin 5 & 6.
USE_STANDARD_LIBRARY_ ADAFRUIT_MOTOR_SHIELD	disabled	Enabling requires additionally 694 bytes program memory.
DO_NOT_SUPPORT_RAMP	disabled	Enabling saves 378 bytes program memory.
DO_NOT_SUPPORT_AVERAGE_SPEED	disabled	Enabling disables the function getAverageSpeed() and saves 44 bytes RAM per motor and 156 bytes program memory.
USE_SOFT_I2C_MASTER	disabled	Saves up to 2110 bytes program memory and 200 bytes RAM for I2C communication to Adafruit motor shield and MPU6050 IMU compared with Arduino Wire.
ENABLE_MOTOR_LIST_FUNCTIONS	disabled	Enables the convenience functions *AllMotors*() and *forAll(). Requires up to additional 80 bytes program space and 7 bytes RAM.

Default car geometry dependent values used in this library

These values are for a standard 2 WD car as can be seen on the pictures below.

Name	Default value	Description
CAR_HAS_4_WHEELS	disabled	Use modified formula for turning the car.
CAR_HAS_4_MECANUM_WHEELS	disabled	Use different setDirection() and modified values for going fixed distances.
DEFAULT_CIRCUMFERENCE_MILLIMETER	220	At a circumference of around 220 mm this gives 11 mm per count.
ENCODER_COUNTS_PER_FULL_ROTATION	20	This value is for 20 slot encoder discs, giving 20 on and 20 off counts per full rotation.
MILLIMETER_PER_DEGREE_DEFAULT	2.2777 for 2 wheel drive cars, 4.1 for 4 WD cars and 2.2 for mecanum wheel cars.	Reflects the geometry of the standard 2 WD car or mecanum cars sets. The 4 WD car value is estimated for slip on smooth surfaces.

Other default values for this library

These values are used by functions and some can be overwritten by set* functions.

Name	Default value	Description
VIN_2_Li-ion	undefined	If defined sets FULL_BRIDGE_INPUT_MILLIVOLT to 7400.
VIN_1_Li-ion	undefined	If defined sets FULL_BRIDGE_INPUT_MILLIVOLT to 3700.
FULL_BRIDGE_INPUT_ MILLIVOLT	6000 or 7400 if VIN_2_Li-ion is defined	The supply voltage used for the full bridge.
USE_L298_BRIDGE	undefined	If defined, sets FULL_BRIDGE_LOSS_MILLIVOLT to 2.0 volt.
FULL_BRIDGE_LOSS_ MILLIVOLT	0 or 2000 if USE_L298_BRIDGE is defined	The internal voltage loss of the full bridge used, typically 0 volt for mosfet and 2 volt for bipolar bridges like the L298.
FULL_BRIDGE_OUTPUT_ MILLIVOLT	(FULL_BRIDGE_INPUT_MILLIVOLT - FULL_BRIDGE_LOSS_MILLIVOLT)	The effective voltage available for the motor.
DEFAULT_START_ MILLIVOLT	1100	The DC Voltage at which the motor start to move / dead band voltage.
DEFAULT_DRIVE_ MILLIVOLT	2000	The derived DEFAULT_DRIVE_SPEED_PWM is the speed PWM value used for fixed distance driving.
DEFAULT_MILLIMETER_ PER_SECOND	320	Value at DEFAULT_DRIVE_MILLIVOLT motor supply. A factor used to convert distance to motor on time in milliseconds using the formula: MillisForDistance = 20 + (RequestedDistanceMillimeter * MillisPerMillimeter * DriveSpeedPWM / DEFAULT_DRIVE_SPEED_PWM)

Compile options / macros for RobotCarBlueDisplay example

To customize the software to different car configurations, there are some compile options / macros available.

Name	Default value	Description
CAR_HAS_VIN_VOLTAGE_DIVIDER	undefined	VIN/11 at A2, e.g. 1 MΩ to VIN, 100 kΩ to ground. Required to show and monitor (for undervoltage) VIN voltage.
VIN_VOLTAGE_CORRECTION	undefined or 0.8 for Uno	Voltage to be subtracted from VIN voltage for voltage monitoring. E.g. if there is a series diode between Li-ion and VIN as on the Uno boards, set it to 0.8.
DISTANCE_SERVO_IS_MOUNTED_HEAD_DOWN	disabled	Distance.h
CAR_HAS_US_DISTANCE_SENSOR	disabled	A HC-SR04 ultrasonic distance sensor is mounted (default for most China smart cars).
US_SENSOR_SUPPORTS_1_PIN_MODE	disabled	Use modified HC-SR04 modules or HY-SRF05 ones. Modify HC-SR04 by connecting 10 kΩ between echo and trigger and then use only trigger pin.
CAR_HAS_IR_DISTANCE_SENSOR	disabled	Use Sharp GP2Y0A21YK / 1080 IR distance sensor.
CAR_HAS_TOF_DISTANCE_SENSOR	disabled	Use VL53L1X TimeOfFlight distance sensor.
CAR_HAS_DISTANCE_SERVO	disabled	Distance sensor is mounted on a pan servo (default for most China smart cars).
CAR_HAS_PAN_SERVO	disabled	Enables the pan slider for the PanServo at the PIN_PAN_SERVO pin.
CAR_HAS_TILT_SERVO	disabled	Enables the tilt slider for the TiltServo at the PIN_TILT_SERVO pin.
CAR_HAS_CAMERA	disabled	Enables the Camera button for the PIN_CAMERA_SUPPLY_CONTROL pin.
CAR_HAS_LASER	disabled	Enables the Laser button for the PIN_LASER_OUT / LED_BUILTIN pin.
ENABLE_RTTTL_FOR_CAR	undefined	Plays melody after initial timeout has reached. Enables the Melody button, which plays a random melody.
MONITOR_VIN_VOLTAGE	disabled	Shows VIN voltage and monitors it for undervoltage. VIN/11 at A2, 1 MΩ to VIN, 100 kΩ to ground.
ENABLE_EEPROM_STORAGE	disabled	Activates the buttons to store compensation and drive speed.

Pictures

Connection schematic of the L298 board for the examples. If motor drives in opposite direction, you must flip the motor to L298 connections.

2 wheel car from LAVFIN with battery case for two 18650 Li-ion batteries, and IR receiver, with power wires in original length.

Connections on the Arduino and on the L298 board.

2 wheel car with encoders, slot-type photo interrupter, 2 Li-ion batteries, Adafruit Motor Shield V2, HC-05 Bluetooth module, and servo mounted head down. 4 wheel car with servo mounted head up. Encoder slot-type photo interrupter sensor Servo mounted head down VIN sensing

Revision History

Version 2.1.0

• Improved examples, especially follower examples.
• Added convertMillimeterToMillis() etc.
• Added Variable computedMillisOfMotorForDistance.
• Added MillimeterPer256Degree and function setMillimeterPer256Degree() instead of using always constants.

Version 2.0.0

• Renamed instance from RobotCarPWMMotorControl to RobotCar.
• MecanumWheelCar support.
• IMUCarData improved.
• Added Voltage handling functions like getVoltageAdjustedSpeedPWM() etc.

Version 1.9.0 - a 2.0.0 pre release

• Removed all *Compensated functions, compensation now is always active.
• Removed StopSpeed from EepromMotorinfoStruct.
• Removed StartSpeed.
• Renamed *.cpp to *.hpp.
• Added and renamed functions.
• IMU / MPU6050 support.
• Support of off the shelf smart cars.
• Added and renamed functions.
• Converted to voltage based formulas.
• Easy configuration of different car features.

Version 1.0.0

• Initial Arduino library version.