Design and Strength Analysis of the Base for Robot Baxter
Abstract
This paper discusses the issue of the subsystem of mobility and solves the design of the lower mobile base for a robot called Baxter. In this paper you can see all the models and parts that are used in construction of mobile base, from which the initial model of the base is created. After making a model of a base, we were putting a load (represents the weight of a robot) on it so we could determine what kind of relative deformations and stresses are created by using finite element method analysis FEM. Later we optimised the base (for example we were changing the length dimensions of some parts), so we could get better results from FEM analysis and also, we wanted the optimised base to acquire similar dimensions and weight as a commercial base. At the end we created technical sheets of all the parts of the base. These technical sheets were later sent to university SIGMA in Clermont-Ferrand (France), from which they constructed mobile base for robot Baxter. FEM analysis was done in program called NX Siemens and models of individual parts were modelled in CATIA V5.
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Introduction
Robots in today’s world plays a very important part. General usage of robots is pretty much used everywhere. They are important in many departments such as engineering, medical, food industry or in various manufacturing processes where these robots are compulsory. Some of these robots have to move from one place to another and this can be provided by subsystem of mobility.
Baxter is a robot that resembles humanoid robot but it is service robot that was created and manufactured in company called Rethink robotics and as a start-up and founder of this company is Rodney Brooks. This robot is used for manual repetitive tasks for example storing, loading, retrieving and sorting which means that this robot can later in future replace human in these simple tasks. Baxter is used in many universities as a teaching aid in the classes of robotics, mechanical engineering and also in many IT departments. It is not required to use any safety requirements while using this robot in comparing with other robots. This robot simply stops when something interrupts its working environment. Only disadvantage of Baxter is that it does not have mobile base which means, it cannot move from one place to another.
The purpose of this article is to design subsystem of mobility for this robot. Company that created this robot is already selling commercial mobile base but it is very expensive where the price of this robot is around 40-thousand dollars. University in Clermont-Ferrand decided to create the mobile base for this robot which is going to be cheaper than commercial base and it is also going to have similar properties than commercial base.
First part of this paper is related to design of the mobile base where the first initial model is going to be loaded by the weight of the robot. Generated strain and deformation were calculated by using FEM analysis in NX Siemens. In the beginning of the FEM analysis we had to define materialistic properties to each model of the base. Later we compared these results with analytical results from selected beam of mobile base where we used method of differential equation of the deflection line to solve bending. In order to solve stresses, it was first necessary to determine the static conditions of equilibrium and determine course of bending moment.
Conclusion
The main task of this work was to create a mobile base for a robot Baxter. At the beginning, there was created a first model of a base which was later modified so that the size and a weight was similar to the commercial base. It was also a priority to save money by creating this mobile base for a robot, as a price of a commercial base for a robot is approximately $40,000 and more. The total cost of this base was around 5,000 €, which saved us a lot of money. This work can of course be continued. Its continuation would be programming the whole system into motion, where for example joystick would be used to control the base itself. Since the base uses simple parts of the drive axle and the question of turning is solved by unidirectional wheel, the mobility can be improved by turning the front wheels as in automobiles.