The idea of building a humanoid robot can sound fascinating to many people but in reality it can be a very intimidating task. In this blog, we explain how to get started with the mechanical system of a humanoid robot and what are the challenges that can be expected along with their solutions.
A humanoid robot is a robot whose appearance and motion is similar to that of a human. In general, a humanoid robot has a torso, two legs, two arms and a head.
A humanoid robot is a complex system which involves concepts of mechanical, electronics, mechatronics and computer science engineering. All the systems work synchronously to perform stable motions. A good approach to deal with a big problem is to break it down and then deal with the individual parts one at a time. Similarly to build a humanoid robot, it would be easier to segregate the system in different part and have a good understanding of how they work individually and how they are supposed to work when put together. In this blog, the discussion will be limited to only mechanical systems.
The first step would be to design the structure of the robot keeping in mind the height of the robot, degrees of freedom (DOF) and materials which would be used to fabricate the parts. There are many software available for designing mechanical parts like Autodesk Inventor, SolidWorks, CATIA, etc.
(Tip: If you are a beginner and this is your first attempt at building a humanoid robot, we suggest that you do not choose a height of over 40 cm and limit the degrees of freedom to a maximum of 20. Remember, greater the height and DOF, the more complex is the system design.)
The thickness of the parts depends on the material selected and strength required. Though metallic parts could provide more strength for lower amount of thickness, they are bound to increase the weight of the robot by some amount. At prototype phase, plastic parts can be easily fabricated using a 3D Printer whereas metal parts have to be furbished at a machine shop.
In our experience, the best approach to design the mechanical system of a humanoid robot is to first define the links and joints and then make a kinematic and dynamic model around them. This model would give a fair idea of the motion profile and the load torque / speed required at every point of the profile. This analysis would also help deciding the nominal torque and speed required for the motor. Further, with these size constraints of the structure and specifications of motor, a suitable servo motor can be selected.
(Tip- Ideally, for a height of about 40 cm, servo motors ranging with a torque between 1.5 Nm to 2 Nm with a load speed of around 60 rpm would work well)
The next step is to have the parts fabricated and assembled along with the motors.
Volla!! The mechanical system of the humanoid robot ready!