Mobile Agricultural Robot : Independent Four Wheel Ackerman Steering
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- Master's theses (IMT) 
The main purpose of this master thesis is to develop the kinematic equa- tions for NMBU Mobile Agricultural Robot. A geometrical approach to nd the kinematic model is proposed. Kinematic constraints is identi ed, and a short discussion whether dynamics can be neglected or not is included. As crab steering is wanted on NMBU Mobile Agricultural Robot, a short discus- sion of the kinematics is presented. Ackerman geometry is introduced, and four wheel Ackerman equations are derived. Curvature and turning radius is used in the kinematic equations, and a singularity condition is both identi ed and taken care of. Kinematic equa- tions are developed further for unambiguous steering angles in all wheel po- sitions and separate equations for all four wheels are presented. A map from signed turning radius to inner and outer side is also found, and this gives us unique kinematic equations. Input like signed turning radius and desired speed in center of robot, outputs correct positions and velocity of all actuated joints. Numerical singularity threshold in singularity workaround are discussed and found. A map from steering angles to number of motor turns is found, as well as a map from ground speed in center of robot to RPM in propulsion motors. An intuitive example where the robot follows a simple path is in- cluded. And in the end, two proposals intended to minimize wheel slip when a vehicle is operating in uneven terrain is shown, and the relevance for these system in NMBU Mobile Agricultural Robot is discussed. A sub-goal is to introduce the concept of mobile agricultural robots, and nd a suitable steering system. Battery as energy source is also discussed, and propulsion, traction and frame of NMBU Mobile Agricultural Robot is mentioned. This is one of ve thesis's forming a project that aims to design and build a working prototype of a Mobile Agricultural Robot.