Lin et al
(back)
Parameters of the Robot (up)
- Di: diameter of the wheels
- n: reduction ratio ([n:1]) of the transmission coupled with each motor of the wheels
- Ce: resolution (ppr) of the encoder coupled with each motor of the wheels
Three-wheeled omnidirectional robot:
- l: distance from the robot's geometric center to the wheels' contact point with the ground
Four-wheeled omnidirectional robot:
- l1: distance between the robot's front and rear wheels
- l2: distance between the robot's left and right wheels
Procedure (up)
- Measure the absolute position and orientation (note: the method requires both position and orientation data) of the robot and initialize the odometry system with that position
- Run the robot through a curvilinear motion in CW direction (ω < 0):
- Set the initial radius (R0) taking into consideration the available space (ω0 = v / R0 or ω0 = vn / R0)
- Set a radius decreasing ration (r%)
- Update the linear velocities of the robot after each l 180º curve (v{l+1} = r% * v{l} or vn{l+1} = r% * vn{l})
- Measure the absolute pose after the robot has gone through 0.5m linear displacement (based on odometry)
- Repeat steps 1-2 if needed (for noise robustness)
- Repeat steps 1-3 in CCW direction
- Repeat steps 1-4 with linear velocity in direction of vn
- Compute the kinematic parameters using the least-squares algorithm
- Adjust the robot parameters given the result from the previous step
Calibration (up)
Matriz Jomni (up)
Note: even though it could be set all the matrices' coefficients unknown, the shapes of Jomni3 and Jomni4 are already known due to the definition of forward kinematics for the three and four-wheeled omnidirectional robots.
Simplified odometry equations (up)
(example for the three-wheeled omnidirectional robot; the four-wheeled is very similar!)
Least-squares algorithm (up)
(three-wheeled omnidirectional robot)
(four-wheeled omnidirectional robot)
(back)