Simple 3-D Manipulator Implementation

I am looking to implement a very simple manipulator arm (say 3DOF). So far, I have just used the example in the rigidBodyTree documentation to display my simple manipulator arm. Now, I want to add some random 3-D waypoints so it can follow a trajectory to a specific end point, and I want to show the animation. How do i accomplish this?

I have no prior experience with MATLAB or mechanics etc. so am looking for the simplest toolsets. I know there is the Robotics System toolbox, and I have heard of the Peter Corke one. I have limited time. Which will be the best option? (I am using the online version of MATLAB.)

Thanks!

Answer 1

[Karsh Tharyani]

It is great to hear from you and I am glad to see your interest in the Robotics System Toolbox. As a starting guide, you can refer to the following blog post https://blogs.mathworks.com/racing-lounge/2019/11/06/robot-manipulator-trajectory/

The Robotics System Toolbox provides several trajectory planning functions which can help in your use case. It sounds like you want your end-effector to follow a certain set of cartesian waypoints. This is commonly referred to as a trajectory in Task Space. Hence, given a certain set of end-effector poses, you would have to use inverse kinematics (IK) to translate this pose to a joint configuration of your robot (this is a row or column vector specifying the position of each revolute or prismatic joint on your robot). The downside with Task Space trajectories is that you call IK for every end-effector pose - and if this is not analytical, the computational times for a trajectory can be high.

You can read about the IK solvers in Robotics System Toolbox here https://www.mathworks.com/help/robotics/ref/inversekinematics-system-object.html

I hope that helps.

[N]

Thank you. I already have a simple manipulator from the examples in the documentation like that of rigidBodyTree. However, it is a stick figure and I don't understand how to make it look like an actual model like the one in thet rajectory link you mentioned. It seems to be using a simulator. How do I get my own defined stick-figure robot to look like that? I am not looking to import another robot's URDF file.

[Karsh Tharyani]

If you want to add visual meshes to your robot’s bodies- please refer to “ addVisual ” function of a “rigidBody”. The robot in the blog post was imported via a URDF which also defines the meshes for the individual bodies.

Hope that helps,

Karsh

[N]

Hello, is there a blog post / video/ example that describes how to generate a path (before generating a trajectory)? I just realized they are two different things, when I read your lin above. I followed an example and created a smple manipulator with axes as per another example, but now I am not sure how to generate a path with respect to the example axis. Thanks.