Experimental validation of flexible robot arm modeling and control

Flexibility is important for high speed, high precision operation of lightweight manipulators. Accurate dynamic modeling of flexible robot arms is needed. Previous work has mostly been based on linear elasticity with prescribed rigid body motions (i.e., no effect of flexible motion on rigid body motion). Little or no experimental validation of dynamic models for flexible arms is available. Experimental results are also limited for flexible arm control. Researchers include the effects of prismatic as well as revolute joints. They investigate the effect of full coupling between the rigid and flexible motions, and of axial shortening, and consider the control of flexible arms using only additional sensors

Perturbation Analysis of Spindle Speed Variation in Machine Tool Chatter

Spindle speed variation has been shown to be an effective method for chatter control. In this paper, a single-degree-of-freedom regenerative type chatter equation is treated using perturbation methods. Rather than using the time coordinate, the angle of revolution is taken as the independent coordinate for maintaining a constant delay in the equations. The spindle speed is taken to be harmonically varying about a constant mean speed. Approximate analytical solutions are sought using the method of strained parameters, a perturbation technique. The amplitude of speed fluctuations (ε) is assumed to be small, and solutions are constructed using this parameter as the perturbation parameter. The stability lobes for constant spindle speeds are calculated exactly. By using the approximate perturbation analysis, the gain in stability is calculated for variable spindle speeds. The analysis is valid for (ε) values up to 0.02 (i.e., 2% of the constant mean speed). Solutions are verified using numerical simulations of the original equation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68588/2/10.1177_107754639700300302.pd

On this issue

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27240/1/0000247.pd

A 21st Century Engineering Education for Leading Concurrent Discovery and Innovation

Keynote PresentationEngineering in the 20th Century has been successful in providing economic, health and security benefits to society. Modern engineering education is the foundation for these advances. However, modern engineering education has not seen major changes since the infusion of engineering science into the curriculum in the 1960’s. Furthermore, a modern engineering curriculum has now become a globally available commodity. Currently the USA awards over 60,000 engineering bachelors degrees per year, the European Union awards over 170,000, Japan awards over 110,000, and major developing nations (i.e., China, Eastern/Central Europe, India) award over 500,000 degrees annually. In the 21st Century we are experiencing an explosion of new knowledge, increasing globalization and significant social and demographic change. It will be essential for engineering to develop the new innovations that benefit society, almost concurrently with the discoveries that enable those innovations. To continue providing benefits to society in the 21st Century, engineering education will need to undergo significant change. This paper argues that we must reinvent the renaissance engineer, based upon sound educational principles, who can provide not only technical expertise but strategic leadership for a highly technological society. The 21st century engineer will first of all need to be an agile and independent learner, who can acquire new knowledge as needed to tackle new problems. The curriculum to support such a transformation will emphasize fundamentals (e.g., science and mathematics,principles of design and manufacturing) as well as the ability to research new topics, skills in communication and teamwork, and strategic, economic, social, artistic, environmental and global perspectives.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106409/1/Roundtable_Ulsoy_CIRP05.pd

Solution of a System of Linear Delay Differential Equations

An approach for the analytical solution to systems of delay differential equations (DDEs) has been developed using the matrix Lambert function. To generalize the Lambert function method for scalar DDEs, we introduce a new matrix, Q when the coefficient matrices in a system of DDEs do not commute. The solution has the form of an infinite series of modes written in terms of the matrix Lambert functions. The essential advantage of this approach is the similarity with the concept of the state transition matrix in linear ordinary differential equations (ODEs), enabling its use for general classes of linear delay differential equations. Examples are presented to illustrate by comparison to numerical methods.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106423/1/ACC_FinalDraft_Submitted.pd

Combined component swapping modularity for a VCT engine controller

The use of bi-directional communication provides additional design freedom which can be used to maximize the swapping modularity of networked smart components. In this paper, application of a design method for combined swapping modularity of two or more system components is discussed. Development of measures for combined swapping modularity is important to be able to analyze more realistic engineering cases. The combined modularity problem is a more difficult problem compared to the individual component swapping modularity problem. First, two approaches (simultaneous and sequential) for combining component swapping modularity of two or more components are presented. Then these combined modularity approaches are used to design controllers which maximize the component-swapping modularity of the Variable Camshaft Timing (VCT) component (i.e. actuator and sensor) and the Exhaust Gas Oxygen (EGO) sensor for an internal combustion engine. Copyright © 2009 by ASME

Swappable distributed MIMO controller for a VCT engine

In the early days of computer control, only one centralized computer was responsible for executing the algorithms. Increasingly, computer control algorithms reside inside individual system components in a distributed fashion. Variable camshaft timing (VCT) is an appealing feature for automotive engines because it allows optimization of the cam timing over a wide range of operating conditions. In this paper, a method to distribute the discrete multiple-input mutiple-output controller for the VCT engine to improve the component swapping modularity of the VCT actuator and the EGO sensor components using network communications is presented. First, a discrete LQG controller is designed, and then this controller is distributed to the engine control unit, the VCT controller, and the EGO sensor controller in order to maximize the component swapping modularity of the system. A control oriented pre-optimization technique, which simplifies the optimization problem, and a candidate solution was devised to maximize component modularity. © 2006 IEEE

An adaptive observer for on-line tool wear estimation in turning, Part II: Results

The basic concept and design of an adaptive observer for tool wear estimation in turning, based on force measurement, has been presented in the previous paper (Part I). This paper shows that numerical problems in the estimation of the states of tool wear precludes the use of this method in multi-wear cases where both flank wear and crater wear are present. The method can be applied, however, when one type of wear (either flank wear or crater wear) dominates. The method is applied in turning experiments to a case where flank wear is dominant, and to a second case where crater wear dominates. For the first case the flank wear estimates show excellent agreement with actual wear measurements. For the second case the crater wear estimates are satisfactory, but not as good as in the first case.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26750/1/0000302.pd

IMPROVING COMPONENT SWAPPING MODULARITY USING BI-DIRECTIONAL COMMUNICATION IN NETWORKED CONTROL SYSTEMS

Increased availability of low-cost electronics has created a new breed of control system components; so called ”smart” components, which can perform control responsibilities in the actuator and sensor components as well as in the controller. ”Smart” components can communicate bi-directionally in networked control systems. We identify opportunities for improving control system performance and design due to the decentralized, yet more connected, nature of these systems. Current research on networked control systems primarily focuses on communication loss and delay of information transfer. This paper investigates the potential benefits of bi-directional communication in a feedback control loop for improving component swapping modularity of the feedback control system. The problem formulation is presented, for the first time, and also illustrated using a driveshaft speed control example.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106389/1/cakmakci_ulsoy_ISFA06.pd

An adaptive observer for on-line tool wear estimation in turning, Part I: Theory

On-line sensing of tool wear has been a long-standing goal of the manufacturing engineering community. In the absence of any reliable on-line tool wear sensors, a new model-based approach for tool wear estimation has been proposed. This approach is an adaptive observer, based on force measurement, which uses both parameter and state estimation techniques. The design of the adaptive observer is based upon a dynamic state model of tool wear in turning. This paper (Part I) presents the model, and explains its use as the basis for the adaptive observer design. This model uses flank wear and crater wear as state variables, feed as the input, and the cutting force as the output. The suitability of the model as the basis for adaptive observation is also verified. The implementation of the adaptive observer requires the design of a state observer and a parameter estimator. To obtain the model parameters for tuning the adaptive observer procedures for linearisation of the non-linear model are specified. The implementation of the adaptive observer in turning and experimental results are presented in a companion paper (Part II).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26748/1/0000300.pd