Inverse Kinematics

Feedback Control Diagram

Here is a position feedback loop diagram, the slider positions read from the pots are fed back to compare with user input so that the slider motors can update the slider positions accordingly. From the Jacobian derived, the x-y position and the rotation angle (theta) of the triangle can be converted to the three slider positions back and forth.

Work space

Path traced by the centroid of the triangle when the 3 links execute their complete range of motion

Circuit Diagram

The Polulu MD06A Dual H-bridge has different pin configurations than the ones other teams have. After consulting the data sheet, here is the circuit diagram hook-up that we figured would work.

Exam Question

Exam Solution

Model

Below is a SolidEdge model of our three degree of freedom system. At each vertex of the triangle sits a ball bearing. Each of these bearings is attached to a foam board rectangle, which is attached to the slider. The slider is mounted onto a foam board riser. Each riser sits on a ball bearing that allows the slider to act as a passive revolute joint.

Project Updates

With no physical system (aside from the sliders), we had to build our own system. We began by thinking about what we could use that would be easy to work with. Foam board was the obvious choice. We began cutting out preliminary pieces and started to assemble our robot.

Initial layout of our system. Attached to the triangle's vertices are the arms that will be attached to the sliders.

Anyone who has used these sliders and solder wires to them knows how important it is to use strain relief (green tape) to lower the chance that the wires will be ripped off.

A fellow group member working diligently to meet Friday's deadline.

Our mounted triangle on the prismatic joints.

Project Description

Initially at the beginning of the semester our group was thinking of using a ping-ball shooter and try to come up the kinematics to allow us to play some typical college games. However, our group thought that would be too cliché and we decided that we wanted something that was more challenging.

After looking through some books and talking with Professor Gillespie, we settled on a three degree of freedom device. The system is to consist of three prismatic joints that will be connected to an equilateral triangle at its vertices. Using the prismatic joints and placing them on ball bearings (allowing them to be passive revolute joints at the same time) we wish to be able to move the triangle to an (x,y) coordinate while also giving it a specific orientation, θ, making this a planar system. We will attempt this by deriving the equations of motions and inverse kinematics.