Mobile Manipulator

This project focused on developing software to control the youBot mobile manipulator, a four mecanum-wheeled base and a 5R robotic arm. The goal was to create trajectory planning, odometry, and feedback control to enable precise end-effector manipulation.

The youBot picks up a block from a specified location, transports it to a target position, and releases it. These capabilities were visualized in the CoppeliaSim simulation environment.

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Project Milestones

1. Reference Trajectory Generation

The end-effector trajectory was defined in eight segments using a combination of CartesianTrajectory and ScrewTrajectory functions from the modern-robotics library.

2. youBot Kinematics Simulator

The kinematics of the youBot were simulated using first-order Euler integration. The inputs included:

• The robot’s current configuration (chassis position, wheel angles, and arm joint angles).
• Joint speeds.

The outputs predicted the next configuration. The transformation matrix for the chassis was computed based on the odometry equations.

3. Feedforward Control

The FeedbackControl function was implemented to compute the kinematic task-space feedforward and feedback control law. This method involved:

• Comparing the current end-effector configuration with the reference configuration at the current and next time steps.
• Deriving the commanded end-effector twist.
• Converting the commanded twist into wheel and arm joint speeds using the pseudo-inverse of the mobile manipulator Jacobian.

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