Design and modelling of a cable driven cart-rail robot for farm automation

Vertical farming is an innovative method to grow crops in constrained spaces and controlled environment. Crop failure is reduced compared to traditional farming. Moreover, with automation, production of crops increases. In the proposed system, a cart rail robot is used to automate different farming tasks. Unlike a conventional system that usually uses rack and pinion or is limited to 1 Degree Of Freedom(DOF) motion, the proposed system uses a cable that actuates the entire motion of the cart providing 2 DOF motion. It works like a Cartesian robot; the motion of the cart is constrained to the XY plane and further constrained to the rail. The paper describes the mechanical design, state-space modeling and analysis of the cart-rail robot. The rails are laid out in columns with a single row. Vertical shelves stacked with crops are kept beside the column rails. A closed loop linear feedback controller was designed using state-space representation and the gains were selected using pole placement method. A study of dynamic system response characteristics for the variation in braking distance due to change in payload was simulated. We have observed that a 1cm position accuracy is achieved. Velocity is limited to the range of 0.1 m/s to 0.2 m/s for the given payload of 25 kg.