RRG Research Robotic Process Modeling

Research:

Process Modeling for Robotic Manipulation

Motivation

There is lack of understanding about tools from the robotic point of view. The robot manipulator has low stiffness which easily allows undesirable deflections in the presence of large reaction force. The effect of tools related to robot configuration parameters is not well understood and there has been little research in the area. Physical tool models for impact should be developed. Robot manipulators have high effective inertia. Inertia of robot manipulators is a function of the robot configuration.

Objective

This research will present physical tool models with robot deflections and will describe tool characteristics and tool wrench/twist behavior in the robotic processes. Robotic processes considered are drilling, deburring, chiseling, sawing, force-fit insertion, forming for assembly, peg-into-hole assembly, screw fastening, and riveting.

Approach

Identify fundamental and analytic parameters of the relevant properties of general robotic processes to develop tool descriptions.
Present robotic tool modeling and the analytical simulations of the motion of tools
Develop process performance criteria for each robotic process and process performance maps of 10 general tools for each process.
Suggest robot manipulation strategies with or without deflections and inaccuracies to avoid process failure such as tool breakage or unstable robot manipulation. Two criteria - wrench/twist transmissibility and impact index - will be discussed.
Implement in-depth simulation for one combination tool and manipulator process.

Robotic Process Parameters and Performance Maps

Considered Robotic Processes:

Material removal processes: drilling, grinding, deburring, chiseling, and sawing.
Assembly processes: force-fit insertion, forming for assembly, peg-into-hole assembly, screw fastening, and riveting.

Robotic Process Parameters: Robotic process parameters can be interpreted as system constants and process variables. Process variables are operating variables and measured variables. Operating variables are inputs of robot controllers. Process performance criteria are outputs of robotic systems and simultaneously affect inputs of robot controllers through on-line or off-line control loops. System parameters define characteristics of robotic systems and system conditions of robotic processes (Fig. 1).

Fig. 1. Robotic Grinding Parameters

Performance Maps: Performance maps for robotic processes are the graphical mapping and parametric descriptions of a considered process performance criteria, which are defined by process operating variables, other process performance criteria, and controllable system parameters. One process performance criteria can be described by other process performance criteria, a vector of process operating variables, and the set of controllable system parameters.

Research Results/Demonstrations

Research Results

Development and analysis of prime performance criteria: wrenches, deflections, specific cutting energy, temperature, tool life/wear, chip thickness, surface roughness, and waviness.
Performance Maps: This research will draw performance maps for each process performance criterion.

Demonstrations

One demonstration of a case study will be implemented to include robot deflections and to find recommended robot configurations by maximum wrench values and a robot stiffness matrix, which will be tabulated on tool tables and drawn on performance maps. The Cincinnati Milacron T3-776 will be used as a robot manipulator for deburring on an automotive workpiece. Compliance matrices of the robot have been defined by Hudgens and Tesar (1992) who measured compliance matrices of Cincinnati Milacron T3-776 industrial robot.