A Rapid Recursive Experimental Approach to Structure/Control Re-Design

This paper introduces an experimental recursive method for simultaneously changing both the mechanical structure and control design of mechatronic systems in order to improve the system’s overall performance. The method improves a system’s closed-loop control specifications through recursive concurrent structure reinforcement and control gain optimization. By using a process of structural reinforcement, a single prototype structure can be used repeatedly until the system performance goals are achieved. To determine the optimal incremental structure changes, a recursive algorithm based on a gradient descent method and a parameter estimation theory is employed. After the incremental structure reinforcements are applied, the control parameters are optimized with respect to multiple control specifications. Next, the resulting system incorporating the structure and control changes is tested and compared with the desired level of performance. The entire process consisting of experimental evaluation, data analysis, and structure reinforcement is repeated until the system performance achieves the desired level. Simulation experiments are successful in changing both the structural and control parameters of a simplified positioning system and show improvement in the system’s overall settling time.

A Probabilistic Tolerance Allocation Method for Dynamic Mechanical Systems With Periodic Response and Discontinuous Forcing Functions

Tolerance allocation standards do not exist for mechanical systems whose response are time varying and are subjected to discontinuous forcing functions. Previous approaches based on optimization and numerical integration of the dynamic equations of motion encounter difficulty with determining sensitivities around the force discontinuity. The Alternating Frequency/Time approach is applied here to capture the effect of the discontinuity. The effective link length model is used to model the system and to account for the uncertainties in the link length, radial clearance and pin location. Since the effective link length model is applied, the equations of motion for the nominal system can be applied for the entire analysis. Optimization procedure is applied to the problem where the objective is to minimize the manufacturing costs and satisfy the constraints imposed on mechanical errors and design variables. Examples of tolerance allocation are presented for a single cylinder internal combustion engine.

Simulation of Automated Robotic Assembly

This paper examines the development of a networked simulation system. The Automated Robotic Manipulation (ARM) simulator is a central part of the network. This simulation tool currently assists with research and education into automated assembly. Robots, fixtures, conveyors, and parts create an automated assembly cell which is used to test advanced manufacturing software. ARM animates models of these physical components and enhances them with additional forms of three-dimensional graphical visualization. The feasibility of automated assembly can rapidly be assessed from the visual content presented by the simulator. Input formats for ARM are flexible enough to support a wide range of assembly cells and activities. Files and network transmissions customize the simulator to a particular assembly cell and its activities. The emerging assembly data protocol promotes the development of a truly integrated manufacturing system. A graphical interface complete with multiple views assists assembly cell layout and activity review, and networked operations significantly expand its role to areas such as interactive robot control and assembly preview.

A Generic Framework for the Integration of Mechanical and Electrical CAD Tools for Concurrent Design of Consumer Electronic Products

Most consumer or commercial electronic products are electromechanical systems consisting of mechanical components such as structures, enclosures, driving systems and mechanisms, combined with electrical components such as printed circuit boards (PCBs), power supply, wires (harness) and switches. The design of such multidisciplinary products involves high coordination and cooperation between the two different engineering fields of mechanical and electrical design. However, in spite of the advancements of CAD tool development in design automation technology within each field, a gap still exists for good communication between the designers in these two fields during the course of the design. This gap makes the design process of such products time-consuming and error prone. This paper describes a research effort that facilitates multidisciplinary concurrent design for consumer electronic products. The focus is on how to integrate mechanical and electrical CAD tools into a more flexible and extensible concurrent design environment to share and communicate critical design information during the design process. A multidisciplinary concurrent design environment based on the CAD framework concept is described. Approaches for integrating the design data and information in such a multidisciplinary design environment are discussed. A prototyping system for the concurrent design of consumer electronic products is also presented.

Parametric Continuity and Smooth Motion Interpolation

This paper deals with the design of a second derivative continuous (C2) motion that interpolates through a given set of configurations of an object. It derives conditions for blending two motion segments with C2 continuity and develops an algorithm for constructing a C2 composite Bézier type motion that has similarities to Beta-splines in the field of Computer Aided Geometric Design. A criteria for evaluating the smoothness of motion is established and is used to synthesize “globally smooth” motions. The results have applications in trajectory generation in robotics, mechanical systems animation and CAD/CAM.

Closed-Form Synthesis of Force-Generating Planar Four-Bar Linkages

This paper presents a technique for synthesizing four-bar linkages to produce a specified resisting force or torque. The resisting energy is provided by a weight acting on the other grounded link. The linkage serves as a nonlinear mechanical advantage function generator. Force and velocity synthesis methods have been extensively discussed in the literature. The general approach, however, has been to assume that the specified force or velocity occurs at a prescribed position. This results in the loss of design parameters that are being used unnecessarily to control position. In this application, force input to the linkage is specified as a function of only the input link position and the magnitude and direction of the weight force. Mechanical advantage synthesis can be achieved at as many as seven precision points. The method presented in this paper allows free selection of two parameters and viewing one infinity of solutions.

Algebraic Representation of Geometric and Size Tolerances

Presented is a method for mathematically modeling mechanical component tolerances. The method translates the semantics of ANSI Y14.5M tolerances into an algebraic form. This algebraic form is suitable for either worst-case or statistical tolerance analysis and seeks to satisfy the requirements of both dimensional metrology and design analysis and synthesis. The method is illustrated by application to datum systems, position tolerances, orientation tolerances, and size tolerances.

Comparison of Assembly Tolerance Analysis by the Direct Linearization and Modified Monte Carlo Simulation Methods

Two methods for performing statistical tolerance analysis of mechanical assemblies are compared: the Direct Linearization Method (DLM), and Monte Carlo simulation. A selection of 2-D and 3-D vector models of assemblies were analyzed, including problems with closed loop assembly constraints. Closed vector loops describe the small kinematic adjustments that occur at assembly time. Open loops describe critical clearances or other assembly features. The DLM uses linearized assembly constraints and matrix algebra to estimate the variations of the assembly or kinematic variables, and to predict assembly rejects. A modified Monte Carlo simulation, employing an iterative technique for closed loop assemblies, was applied to the same problem set. The results of the comparison show that the DLM is accurate if the tolerances are relatively small compared to the nominal dimensions of the components, and the assembly functions are not highly nonlinear. Sample size is shown to have great influence on the accuracy of Monte Carlo simulation.

Design for Manufacturability

Research has been carried out at Coventry University Centre for Integrated Design on the concept design process and it is funded by the Coventry University Research Fund. An experiment, simulating product design in industry, was conducted by concept designers which were, in turn, acted by student industrial designers and student engineering designers. In general the product design process is a sequential process. The first part of the process is the conceptual phase. This is followed by the engineering design phases which include all the manufacturing information. In this case the downstream engineering design focuses on designs for manufacture and process selection. Information on the requirements of conceptual designers in these areas was collected from these experiments. The information is ultimately to be incorporated into rules in a knowledge base which can be readily accessed by the industrial designer during concept development via a CAD system.

Exploratory Investigation of Layered Fabrication Applied to Construction Automation

After more than a decade of research in construction automation, robotic tools have brought little if any productivity improvement to the industry. In this paper, we argue that automation which applies to most manufacturing industry does not translate effectively to construction which is limited not by labor, but by process. We propose a radical departure from generally accepted concepts in construction automation and demonstrate that new techniques of layered manufacturing can be applied effectively to construction. In the process, we also modified material processing of cement to adapt it to the requirements of rapid prototyping. We illustrate our purpose with sample structures manufactured by incremental deposition of reactive bulk materials (cement and Silica in this instance).