Download - Workspace design
Workspace design of robots
-Nishant Iyer
What is a robot?
• A robot is a mechanical intelligent agent which can perform tasks on its own, or with guidance.
• It is usually an electro-mechanical machine which is guided by computer and electronic programming.
Some examples to understand them more
What is degree of freedom?
• It is the total number of independent motions that can be performed by a rigid body.
• Lets understand this in a little more detail.
Lets understand DOF
• Any free body in 3D space can perform translation and rotation along x , y and z axes.
• Just imagine a brick floating without gravity.
• This accounts to a total of 6 DOF.
What does DOF depend on?
• A maximum of 6 DOF is possible for any rigid body.
• Now the degree of freedom depends on the kind of joint and constraints on a robot.
• Different joints give different DOFs.• Lets see some examples.
Types of joints and their DOFs
• A pin joint gives a single degree of freedom as it permits rotation only along the pin axis.
• A ball and socket joint gives 3 DOFs as it allows rotational motion along the three axes. Translation motion is restricted in this.
Understanding workspace
• To understand workspace , lets consider a cylindrical configuration robot.
• This has the capability to perform linear motion along z and y axes.
• It also rotates along the z-axis.
• This its DOF will be 3.
Understanding workspace
• This is how its workspace/work volume be like.
• Lets work out step by step how this came about. Workspace of a
cylindrical configuration robot
Step by step formation of a workspace/work volume
• Keeping y co-ordinate at its maximum value, and tracing the path of a point on end effector by rotating only along z-axis, we get the shown curve.
• Similarly keeping the y co-ordinate minimum, we trace the smaller inner curve.
• This is the workspace of the robot along just 2 DOF. i.e. rotation along z-axis and translation along y-axis.
Finally the workspace is obtained
• Now this robot can perform translation motion along z-axis.
• Hence we extrude the one dimensional figure along the z-axis till the maximum value is reached.
• This gives us the three dimensional workspace of the robot.
Why is knowledge about work volume important?
• The work volume defines the total volume swept by the end effector of a robot.
• In industrial assembly lines there will be many robots and components nearby to each other.
• Its upto us to programme the motions of the links of the robot such that there are no collisions.
How can it be controlled or designed?
• The work volume can be designed as per requirements.
• This is possible by controlling the movements of links by setting maximum values to the actuators at the joints.
• The maximum values have to be set according to the obstructions around the robot.