Robi

Drew Coverdill

Ken Heinz

GE423, Spring 2008

Ken and Drew were graduating seniors in mechanical engineering. Our Robot, affectionately called “Robi,” was the product of many lonely nights in the lab as the sole group of two. Through excellent teamwork and ingenuity, we created a robot worthy of its second place finish.

Figure 1: The Creators- Ken Heinz (left) and Drew Coverdill (right)

Key Points:

• Custom designed and fabricated single-servo “finger” can gripper

• Precision Machined parts using tabletop mill with G code

• Two bay ball repository

• State machine and double state machine C code

• Modified vision code

• VB application

The “finger” gripper was modeled after the bone and tendon structure of the human finger, with kite string used as the tendons. The gripper was designed in ProE and fabricated preassembled using the Objet Rapid Prototyping machine in the MechSE Ford Lab. Other components were cut from PVC or plexiglass on the tabletop mill, using computer control and G code for precision and repeatability.

Figure 2: Gripper arm modeled in ProE

We used only one servo in the can gripper, while still lifting the can off the ground. Picking the can up allowed for the collection of golf balls while holding the can, and thus faster completion of the course. The need for only one servo in the gripper allowed for the remaining two servos to independently control the ball bay doors.

Video of “Robi” picking up the can

Figure 3: Front view with can up and all balls collected

The two bay ball repository allowed collection of the orange and blue balls simultaneously, while letting them to be discharged separately into their respective bins. We were able to complete the course in one pass, depositing the can and collecting all the balls, resulting in the record low time of 57.16 seconds.

Video of “Robi” picking up balls

Video of “Robi” running the course

Figure 4: Orange Side

Figure 5: Blue Side

A state machine was used to control the robot’s actions, and for the more complicated actions, a second state machine was used within the state to further break down the code while keeping it understandable. By using the state machine our robot was able to complete the course equally well running counter clockwise or clockwise, with very little additional code required.

The Vision code was heavily modified. Changes included: detecting multiple colors simultaneously (still 1 color per frame), variable size (2x vs 4x), image location (for 2x), top cutoff, and bottom cutoff for each color, thresholded output to color LCD screen, and display of all centroids on color LCD screen in every frame. These changes allowed for excellent vision based tracking of the can, golf balls, and lights. We were proud to be able to see the third light even in its highest position.

The Visual Basic Application was nothing particularly fancy, but did track the where Robi though he was, the current integrated and compass angle, and allowed us to start the robot, move the gripper, change the initial position, and many other parameters, all with the click of a button instead of the agony of flashit. Finally, Robi times his own runs, for convenience.

Link to .zip file of all VB and C code

Figure 6: VB Interface