Bangalore Mirror ||
Robotic engineers at IISc have designed a wheeled mobile robot that can move in a stable manner on an uneven terrain with minimal slipping. Prof Ashitava Ghosal from the Department of Mechanical Engineering, IISc, Bengaluru and Tharakeshwar Appala from SSJ Engineering College, Hyderabad have demonstrated a prototype of an “autonomous mobile robot” that can travel in a straight line, make turns and also switch lanes on a bumpy terrain, with minimal slipping. Autonomous mobile robots are capable of navigating unknown and unstructured environments, and have the capability of negotiating rough terrains with minimal intervention from human operators. This makes them suitable for activities such as household cleaning, delivering goods and services, and planetary exploration. NASA’s ‘Curiosity’ Mars rover, an example of an autonomous mobile robot, is currently exploring the surface of Mars and has detected minerals which indicate existence of water on the Martian surface in the past.
A common problem with these robots is slip at the wheel-ground contact. “A problem that will need some looking into in wheeled mobile robots is Simultaneous Localization and Mapping. A mobile robot must know its location and be able to make a map of its environment to operate autonomously. An odometer — an instrument to measure the rotation of the wheel — is used to obtain the robot’s location. When a wheel slips, the robot’s location is unchanged and this leads to localisation errors,” explains Ghosal. He also notes that wheel slip leads to power wastage. Wheel slips can also lead to unstable motion and the robot can tip over on the uneven terrain. Motivated by this challenge, the team at IISc focused on designing robots that do not slip and are stable over such terrains.
In the proposed design, the robot consists of one front wheel and two torus-shaped rear wheels. The wheels are designed to always keep contact with the ground and they are driven by motors. The rear wheels are connected to the platform through a suspension mechanism having four links. Two of the links are fixed and the other two are free to move at an angle. This enables lateral tilting of the wheel, thus preventing a slip. The wheels are coated with rubber to enhance friction. The team also tested the prototype to assess its functionality. They simulated the functioning of the robot with Adams — a software that enables users to provide arbitrary inputs to simulate the motions of a robot. The robot’s performance was assessed for three types of desired paths: straight line, a circular motion of 30° and a lane change. With the new design, the team observed 50% reduced slippage in comparison with previous models. The applications of such autonomous wheeled robots are enormous. “A rover called ‘Opportunity’ sent by Nasa has been operating successfully in exploring Planet Mars for more than seven years now. In my opinion, apart from planetary missions, the wheeled robots will find increasing use in industry and security-related applications in India,” said Ghosal. With India’s Mangalyaan and Chandrayaan making strides and plans to send a rover to the moon for exploration, this research work may complement the country’s journey into space. – Courtesy