68 lines
3.4 KiB
Markdown
68 lines
3.4 KiB
Markdown
# kinematics
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Arduino Kinematics library for differential drive(2WD, 4WD) and mecanum drive robots.
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The library requires the following robot's specification as an input:
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- Robot's maximum RPM
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- Distance between wheels (Front-Left and Front-Rear )
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- Wheel's Diameter
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## Functions
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#### 1. Kinematics::Kinematics(int motor_max_rpm, float wheel_diameter, float base_width, int pwm_bits)
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Object constructor which requires the robot's specification.
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- MOTOR_MAX_RPM : Maximum RPM of the motor
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- WHEEL_DIAMETER : Robot wheel's diameter expressed in meters
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- FR_WHEEL_DISTANCE : Distance between front wheel and rear wheel
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- LR_WHEEL_DISTANCE : Distance between left wheel and right wheel
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- PWM_BITS : PWM resolution of the Microcontroller. Arduino Uno/Mega, Teensy is 8 bits by default
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#### 2. output getRPM(float linear_x, float linear_y, float angular_z)
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Returns a Vector of Motor RPMs from a given linear velocity in x and y axis and angular velocity in z axis using right hand rule. The returned values can be used in a PID controller as "setpoint" vs a wheel encoder's feedback expressed in RPM.
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- linear_x : target linear speed of the robot in x axis (forward or reverse) expressed in m/s.
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- linear_y : target linear speed of the robot in y axis (strafing left or strafing right for mecanum drive) expressed in m/s.
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- angular_z : target angular speed of the robot in z axis (rotating CCW or CW) rad/sec.
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#### 3. output getPWM(float linear_x, float linear_y, float angular_z)
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The same output as getRPM() function converted to a PWM value. The returned values can be used to drive motor drivers using the PWM signals.
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#### 4. velocities getVelocities(int motor1, int motor2)
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This is the inverse of getRPM(). Returns linear velocities in x and y axis, and angular velocity in z axis given two measured RPMs on each motor of a 2WD robot. The returned values can be used to calculate the distance traveled in a specific axis - where distance traveled is the product of the change in velocity and change in time.
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- motor1: left motor's measured RPM
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- motor2: right motor's measured RPM
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*each motor's RPM value must be signed. + to signify forward direction and - to signify reverse direction of the motor.
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#### 5. velocities getVelocities(int motor1, int motor2, int motor3, int motor4)
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The same output as No.4 but requires 4 measured RPMs on each motor of a 4WD robot. This can be used for both 4 wheeled differential drive and mecanum drive robots.
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- motor1: front left motor's measured RPM
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- motor2: front right motor's measured RPM
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- motor3: front right motor's measured RPM
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- motor4: front right motor's measured RPM
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*each motor's RPM value must be signed. + to signify forward direction and - to signify reverse direction of the motor.
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## Data structures
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#### 1. output
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Struct returned by getRPM() and getPWM used to store PWM or RPM values.
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```
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struct output{
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int motor1;
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int motor2;
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int motor3;
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int motor4;
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};
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```
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* each returned motor RPM or PWM value is signed to signify the motor's direction. + forward direction ; - reverse direction.
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#### 2. velocities
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Struct returned by getVelocities() used to store linear velocities in x and y axis, and angular velocity in z axis (right hand rule).
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```
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struct velocities{
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float linear_x;
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float linear_y;
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float angular_z;
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};
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```
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* linear_x and linear_y are expressed in m/s. angular_z is expressed in rad/s
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