Tire and Wheel Assembly Robot

This project was my most challenging to date and caused to me to draw on my innovation skills and also my ability to incorporate new technology with old outdated technology. I was introduced to the world of Robotic Automation thru the task to build a Pick and Place Assembly Robot in 2011. I was tasked with integrating a retired robot welder at the end of its useful life with a Vision System combining robotics and automation. In doing my research for this project I discovered that there was not an existing body of knowledge on this topic that was easy to draw from. I inquired in PLC and Automation forums and found very little insight. I discovered that I was on my own in this endeavor and was probably the only person or one of the few working on this configuration of MRC and Vision Guided Robotics in the USA. At this point, our local Integrator had not progressed to Visions Guided Robotics and I was pushing the envelope. The end result was to be a system in Vision Guided Robotics assembling a wheel and tire assembly on a fixture. The first piece of this project that I became aware of was Motoman MRC welding robot Circa 1994 that was retired from welding service after a long service life. This robot was near 17 years old at the time. The next part of the project was a Camera system from Teledyne Dalsa- the VA21 system. Along with the camera I received inspection camera software called Inspect from Teledyne Dalsa that I needed to educate myself on. As I learned to use the Inspect software I came to appreciate the usefulness of this package. So I had to study this problem from many angles. I discovered that I would have to pass XY coordinates from the Camera Controller to the MRC robot controller by RS232 Serial Cable because that was the only way to accomplish this task since the MRC only had a Serial Port available. So I manually assembled all the RS232 serial cables that were required for this system. This system would be responsible for assembling several different wheel bearing and spacer combinations. Each particular size of the wheel would require different configurations on the Camera Controller. Different configurations of the assembly required different combinations of bearings, spacers and wheel assemblies. The Teledyne Dalsa engineer told me that each particular configuration in the Camera Controller is called a Solution. This would indicate that different wheel assemblies would require different Solutions on the Camera Controller.

The general order of the assembly process for the robot was as follows:

The Vision System locates the center of a wheel assembly using Feature Search.
The robot grabs a bearing and puts it on the assembly spindle.
The robot grabs a spacer and puts it on the assembly spindle.
The robot grabs a tire and wheel assembly and places it on the assembly spindle.
The robot grabs the second bearing and puts it on the spindle.
The hydraulic press swings into place and applies hydraulic pressure to the wheel assembly to press the bearings into place.
The robot grabs the completed tire assembly and passes the assembly over a proximity switch to verify that the bearing is installed properly on the wheel assembly.
If the proximity switch test is passed the completed tire assembly is put into a tub.

Four cell phone videos are included to show the operation from various angles.

COMPONENTS

DO-06DR

I use this PLC because it has universal inputs for sourcing and sinking and relay outputs so that almost any combination of inputs and outputs are usable. The PLC communicates with the MRC Robot and the Hydraulic Press in the Assembly fixture by Digital I/O and communicates with the Camera Controller by Ethernet. The PLC loads the proper Solution in the Camera Controller for the tire assembly being built by commands sent over a Modbus link.

VA21

The VA21 series Camera Controller from Teledyne Dalsa is a robust and very configurable Vision Appliance for use with a machine vision camera. The Inspect software loaded into the Controller reads the X and Y coordinates of the wheel spindle and sends them to the MRC Robot by RS232 Serial Cable.

MICRO HMI

The assembly information for each wheel was contained in a recipe. The Micro version of C-MORE HMI will load the registers in the PLC with the predetermined recipe for each wheel assembly. Each recipe loads the proper job in the MRC Robot and loads the proper Vision Solution in Camera Controller for the assembly being built.

MOTOMAN MRC ROBOT

This is a Motoman MRC Robot system. These were built in the timeframe of 1994. The Motoman Robot memory contained the jobs for each specific wheel assembly. The jobs are loaded by Digital I/O commands from the PLC. The LoadV and SaveV commands from the Motoman controller became very important to load the controller jobs.

VIDEOS OF ROBOT IN OPERATION

BLOCK DIAGRAM

INSPECT SOFTWARE IN OPERATION

This is Inspect Software from Teledyne Dalsa in operation showing a layer of wheel assemblies ready for the assembly operation to begin. As you can see the Feature Finding Tool of the software has located a spindle center and has determined the X and Y coordinates of the pick. These X and Y values are communicated from Camera Controller thru RS232 Serial Cable to the MRC Robot. Variables were used to hold the X and Y values that the Vision Camera gathered by scanning the center of the wheels. I used my coding skills to translate these variables from the Vision Camera into Motoman variables that could be communicated to the MRC Robot via the RS232 Cable. When the wheel has been removed from the group the software looks for the next spindle center and the sequence continues. When an entire layer of tires has been removed the hydraulic platform raises the pallet of tires to make the next layer available to the robot.

Inspect software has other uses on the factory floor. These uses include positioning, identification, verification, measurement and flaw detection.