Duration: Jan 2019 - May 2019
Purpose: Independent project conducted at Birla Institute of Technology and Science, Pilani, under the guidance of Prof. Y. V. Daseswar Rao
Skills: Raspberry Pi, Python3, OpenCV 3.0, Sockets, Tkinter GUI, Image Processing
This project is part of a long term project to create a fully autonomous rover capable of carrying messages, documents or small parcels across the college campus. Such a rover would need to travel across floors and through multiple indoor and outdoor areas, requiring it to traverse obstacles such as stairs, steps, ramps and uneven ground. This project focuses on one part of this, to climb and descend staircases.
Approach
We (team of 2) decided to use the Rocker Bogie mechanism for the rover. The Rocker Bogie mechanism is a very versatile configuration used by NASA's Curiosity rover on Mars that allows it to traverse over obstacles much larger than the size of it's wheels, unlike traditional fixed wheel rovers. This makes it ideal for stair climbing applications. In addition, wheels on either side of the rover move independently of each other, making travel over uneven surfaces very smooth.
Our rover was designed to climb a typical staircase with each step 15cm high and 40cm wide. The design is shown below. It was fabricated using Acrylic sheets and a CNC machine.
Climbing Stairs
The rover executes a three stage ascent with the front wheels pulling the rover up and forward and the back wheels pushing against the front to provide enough traction allowing the front wheels to climb the vertical surface.
Descending Stairs
Challenges Faced
Climbing a vertical surface requires good traction between the wheels and the ground. However, the rubber tread on the wheels were unable to provide enough grip, leading to significant slippages. This was mitigated to some extent by using softer rubber and increasing the torque of the driving motors, however the rover still faces slippage at the start of each step. Improving the tread of the wheels and further increasing the torque would enable the rover to climb smoothly.
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