This paper presents new active control strategies to prevent heavy vehicle rollover and focuses mainly on cases of maneuver-induced rollover such as rollover in cornering and lane-change maneuvers. Two performance measures as control strategies are explored: the lateral load transfer ratio and the trailer lateral acceleration. A nonlinear 75,000 pound 5-axle tractor/semitrailer computer simulation model has been used to demonstrate the effectiveness of the proposed active control system. A new non-linear sliding mode controller has been designed and found to be effective in improving the dynamic performance and roll stability, regardless of parameter uncertainties, such as tires or suspension characteristics. The controller torque requirement is limited by the differential dynamic braking forces that the tractor drive axles are able to produce as a function of the applied dynamic loads and road surface condition. The results show that with this new controller, the vehicle lateral acceleration can be controlled to prevent rollover without significant change of the vehicle trajectory when active yaw torque is applied to the tractor drive axles. Also, simulation results indicate that the vehicle rollover might be prevented using either the lateral load transfer ratio or the lateral acceleration at the trailer centre of gravity as control strategies.

This paper describes the design and characterization of monolithic clamping structures for mechanical packaging of optical fibers in optical MEMS devices. Both single crystal silicon and nickel LIGA components have been investigated [1,2]. Mechanical clamping methods for optical fiber integration were perused both for on-chip attachment as well as alignment-assist in conjunction with other packaging methods. Arrays clamps with normal clamping forces ranging from 3mN to 375mN were designed, fabricated and characterized. A detailed theoretical analysis of clamping force for each design is presented and compared to measured results from fabricated devices. The clamps were evaluated on their ability to maintain alignment under a range of mechanical and thermal loads. Four arrays of eight clamp sets with varying applied normal clamping forces were designed by varying the deflection of 10μm and 20μm cantilever beams, and arranged in single-clamp and double-clamp configurations. A 100μm moment arm, integrated into the clamp structure, permitted the cantilevers to be initially deflected by the inserted fiber face during the fiber channel population. The populated test clamp arrays were heated from ambient conditions to 55 degrees Celsius to assess their stability under thermal strain, and monitored with an integrated Fabry-Perot whitelight interferometer. The maximum induced axial misalignment did not exceed 3μm. In addition to current theoretical and experimental results, alternative mechanical fiber clamp designs for both silicon and nickel microfabrication are presented and analyzed.

Front-end structural concepts used to enhance the crash energy management of a sport utility like aluminum vehicle are discussed in this paper. These structural concepts were applied to the front-end rails, subframe, and subframe extension. Epoxy-based foam reinforcement was applied to the 5754 aluminum front end rails, shearing was applied to the cast-hydro formed tubular subframe, and a new load path was implemented in the front end structure in the form of a subframe extension. Deceleration-time response was developed and benchmarked against target double plateau square pulse at the early stage of the design. Vehicle front-end design and analysis for US-NCAP 35 mph full frontal crash were conducted using concept and detailed nonlinear finite element codes. Concept modeling tools that were used in the initial design stages involve collapsible nonlinear beam finite element, strength and stability, and spring mass system codes. Detailed finite element code RADIOSS was applied to the analysis of the final front-end structural design. Occupant responses and injury numbers were evaluated using MADYM03D rigid body and finite element code. Concept vehicle crash safety protection was evaluated and star-rated then benchmarked against 2000 and 2001 production SUVs. A paper study was conducted on a higher strength less ductile 6111T6 stamped aluminum alloy to further enhance the structure and enhance dash and floor intrusion. Structural collapse mode, deceleration-time response, and occupant simulation results show a good performance of aluminum front-end structures in managing crash energy and protecting vehicle occupants.

The lateral stability of railroad vehicles travelling on tangent tracks is one of the important problems that has been the subject of extensive research since the nineteenth century. Early detailed studies of this problem in the twentieth century are the work of Carter and Rocard on the stability of locomotives. The linear theory for the lateral stability analysis has been extensively used in the past and can give good results under certain operating conditions. In this paper, the results obtained using a linear stability analysis are compared with the results obtained using a general nonlinear multibody methodology. In the linear stability analysis, the sources of the instability are investigated using Liapunov’s linear theory and the eigenvalue analysis for a simple wheelset model on a tangent track. The effects of the stiffness of the primary and secondary suspensions on the stability results are investigated. The results obtained for the simple model using the linear approach are compared with the results obtained using a new nonlinear multibody based constrained wheel/rail contact formulation. This comparative numerical study can be used to validate the use of the constrained wheel/rail contact formulation in the study of lateral stability. Similar studies can be used in the future to define the limitations of the linear theory under general operating conditions.

In this paper, modified truck designs were studied with an objective to achieving better compatibility between high speed stability and curving behaviour compared to the conventional truck. The analysis has shown that USD truck can be designed to achieve better over all performance compared to other truck designs. The results of steady state curving program were validated using the commercial software package NUCARS. The comparison of steady state curving behaviour of different truck designs using NUCARS also showed that USD truck has the potential to achieve superior performance compared to other truck designs. The research reported in this paper has dealt with steady state curving behaviour. To look into the safety implications of the new designs, transient behaviour in curves must be studied. The response of the railway cars in entry and exit spirals should be evaluated. The effects of track irregularities on the response of these modified designs need to be analyzed.

A stable strain feedback control design is proposed for a flexible two-link manipulator using a model with partial differential equations directly. Stability is established using a Lyapunov-based design.

A control strategy is presented which reduces destabilizing effects of unmodeled higher-order dynamics found in many systems subject to control. These effects are major limiting factors of conventional controllers, especially for high-performance machinery, such as precision machine tools and robotic manipulators. In the proposed strategy, a substitute feedback signal is synthesized in order to extract dominant dynamic components (e.g., rigid body motion of a flexible robotic manipulator) from the output of the controlled system. A unique arrangement of a band-limited state observer and a low-pass filter corrector is employed for this purpose. The synthetic signal is used as a controller input, effectively eliminating destabilizing effects of unmodeled dynamics of the controlled system. A simulation example demonstrates that the strategy results in improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to conventional methods adopted currently in engineering practice.

Observer-corrector feedback is a control strategy which reduces destabilizing effects of unmodeled higher-order dynamics (e.g., structural resonances of a robotic manipulator) found in many systems subject to control. The fundamental idea is to synthesize a substitute feedback signal in order to extract dominant dynamic components (e.g., rigid body motion of a robotic manipulator) from the output of the controlled system. A band-limited state observer complemented by a low-pass filter corrector are employed for this purpose. The synthetic signal is used as a controller input, effectively eliminating destabilizing effects of unmodeled dynamics of the controlled system. In the presented work, the observer-corrector feedback mechanism is implemented for motion control of a three-axis direct-drive robotic manipulator for automated pick-place operations in semiconductor manufacturing applications. A detailed technical description of the robotic manipulator is provided, a control system with the observer-corrector arrangement is designed, and selected results of laboratory tests are presented. The tests demonstrate that the observer-corrector feedback mechanism leads to improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to usual control methods.

A fuzzy system and the control algorithms are proposed to solve the control multi-chain robotic system formed by tentacle manipulators grasping a commune object with hard contact points. The control system contains two parts: the first component is a conventional controller, which implements a control strategy based on the Lyapunov stability, and the second is an adaptive fuzzy controller which adjusts the control parameters by the output of the first level controller. The stability and robustness is investigated and the fuzzy rules are established The fuzzy controller was developed using Matlab and Simulink software. Simulation results are presented and discussed.

In this paper we present further results on adaptive compression braking control for a Class-8 heavy duty vehicle with the objective to achieve good and consistent vehicle speed tracking performance during large variation in vehicle mass (payload) and road grade. In our previous work the adaptive controller performance was tested in simulations on a reduced order nonlinear vehicle/engine model. In this paper, we include several modifications to deal with actuator saturation and unmodeled dynamics. The final version of the controller is successfully evaluated on a high order crankangle model. Good tracking performance during braking as well as estimation properties of the algorithm for vehicle mass and road grade are confirmed. Moreover, the stability and response properties of the overall scheme are rigorously analyzed.

This paper addresses the stability of traffic flow on a highway when the vehicles operate under an adaptive cruise control (ACC) system. ACC systems are commonly designed to maintain a constant time-gap between vehicles during vehicle following. Previous researchers in literature have produced contradictory results on whether the traffic flow is stable when the constant time gap spacing policy is used. This paper resolves the contradiction and shows that the boundary conditions used at the inlets and exits influence traffic flow stability in the case of the constant time-gap policy. Further, the paper shows that it is possible to design an unconditionally stable spacing policy, i.e. a spacing policy which guarantees traffic stability under all boundary conditions. The practical implications of instability are shown through traffic simulation results. The advantages of an unconditionally stable spacing policy over the constant time-gap policy are demonstrated. The answer to the question “Should ACC systems be designed to maintain a constant time gap between vehicles?” is NO. It is quite easy to develop alternate spacing policies with superior stability properties.

This paper presents a rigorous analysis and design method for PWM-based control of pneumatic systems. An equivalent analytical model incorporating the effects of a finite PWM switching period is formulated. This equivalent model was motivated by a lack of control design and analysis techniques needed to treat the inherently non-analytical switching models associated with PWM-based systems. The equivalent model enables the design of a loop compensator that rigorously addresses control design issues of stability robustness, disturbance rejection, insensitivity to sensor noise, performance bandwidth and actuator saturation. Simulation of this compensator with both the equivalent design model and a full nonlinear switching model for a particular pneumatic robot application is presented which demonstrates and validates the proposed method.

Active counter-force vibration control has significant advantages over the more traditional motion-based active vibration suppression schemes. A piezoelectric ceramic (PZT) inertial actuator is an efficient and inexpensive solution for this type of structural vibration control. In order to properly tune the control parameters of the absorber subsection, an accurate mathematical model is necessary. For this, a nonlinear model for the PZT inertial actuators is presented. In particular, a polynomial form of non-linearity in the dynamical model of the actuator is assumed. An inverse problem is then formed to identify the model parameters of the actuator (absorber). The model parameters consist of the effective mass, damping and stiffness of the actuator as well as the polynomial form of the non-linearity. Using Lyapunov’s second method, the stability conditions for the proposed nonlinear model are established. An experimental setup is developed to validate the proposed nonlinear model. The results of the model identification using the actual experimental data demonstrate that the nonlinear model would better fit the experimental data, when compared to the linear model.

A novel dynamic vibration absorber is presented while exploring its practical implementation using piezoelectric ceramic (PZT) inertial actuators. It is referred to as active resonator absorber (ARA). The ARA is a passive absorber with an additional dynamic feedback compensator within the PZT actuator. Without any controller, the PZT inertial actuator becomes a passive vibration absorber due to the internal damping and stiffness properties of piezoelectric materials. Hence, it is inherently fail-safe. For active operation, the compensator parameters are designed such that a resonance condition is intentionally created within the absorber to mimic the vibratory energy from the system of concern to which it is attached. The resonance condition can be created through the appropriate design of the compensator and implemented through adjusting the external electrical voltage applied to the absorber. Because the parameters of the PZT actuators (i.e. stiffness, damping, and effective mass) are estimates, compensator designs based on these parameters would result in partial vibration suppression, when utilized in real applications. An auto-tuning method is, therefore, introduced to effectively tune the compensator parameters to improve vibration suppression quality. The effectiveness and stability of the proposed absorber is demonstrated through simulations when appended on a SDOF primary system.

This paper presents a stability analysis of a continuously controlled adaptive tuned vibration absorber (ATVA) incorporating shape memory alloy (SMA) structural elements to realize attenuation of the vibration of a primary system subject to uncertain tonal excitation. The objective is for the SMA ATVA stiffness to be adapted such that a relative phase angle of −90° is achieved between the vibration of the SMA ATVA and the primary mass. The Lyapunov-based stability analysis indicates that the system is stable under proportional-plus-integral control across the operating range of the SMA ATVA when an integral reset is included in the control algorithm. The integral reset also substantially improves the performance of the system when compared to the original PI controller without reset.

This paper presents an influence region analysis for an actively tuned vibration absorber, the Delayed Resonator (DR). DR is shown to respond to tonal excitations with time varying frequencies [1–3]. The vibration suppression is most effective at the point of attachment of the absorber to the primary structure. In this study we show that proper feedback control on the absorber can yield successful vibration suppression at points away from this point of attachment. The form and the size of such “influence region” strongly depend on the structural properties of the absorber and the primary system. There are a number of questions addressed in this paper: a) Stability of vibration absorption, considering that a single absorber is used to suppress oscillations at different locations. b) Possible common operating frequency intervals in which the suppression can be switched from one point on the structure to the others. A three-degree-of-freedom system is taken for as example case. One single DR absorber is demonstrated to suppress the oscillations at one of the three masses at a given time. Instead of an “influence region” a set of “influence points” is introduced. An analysis method is presented to find the common frequency interval in which the DR absorber operates at all three influence points.

This paper analyzes the problem of Co-Simulation. The term Co-Simulation is used to describe a large dynamic system that is simulated by running a group of independently coded subsystem simulators. Very commonly, the Co-Simulation of subsystems faces incompatible boundary conditions, i.e., causal conflicts. These causal conflicts cannot be directly resolved, due to the nonlinearity and/or difficulties in modification of coded subsystem simulators. Causal conflicts result in algebraic constraints. Boundary Condition Coordinators (BCCs) are designed to calculate boundary conditions based on subsystem models and their algebraic constraints. The Co-Simulation, which is modeled as Differential Algebraic Equations, then relies on BCC to provide compatible boundary conditions for subsystem simulators. The high index constraint is reduced to index one by defining a sliding manifold. Different ways of enforcing the sliding manifold are discussed: A new Discrete-Time Sliding Mode (DTSM) controller is devised to serve as a BCC, enforcing sliding manifolds and providing boundary conditions. The multi-rate scheme can guarantee Co-Simulation stability at any given step size of all subsystem simulators, provided the subsystem simulators are tested stable at that step size. An example is given to demonstrate the DTSM method. Advantages and possible future improvements are discussed.

This paper presents preliminary investigations into a novel approach to circumventing a classic tradeoff between robustness and performance in Iterative Learning Control. The tradeoff is usually performed by designing an appropriate filtering mechanism to compensate for non-perfect resetting and noise. Time-Frequency analysis is used to examine the frequency content of error signals over the compact time support of the reference signal. This then allows the filter to effectively change its bandwidth as a function of time thereby allowing high frequency system dynamics to enter into the learning process at the appropriate time instants. At the same time, robustness is maintained by reducing the bandwidth of the filter when the system dynamics do not exhibit high frequency characteristics so as to attenuate the effect of noise on the learning stability. This Adaptive Iterative Learning controller is needed for systems that have non-smooth nonlinearities and the advantages are demonstrated here in simulation and experiment.

A direct adaptive control framework for a class of nonlinear matrix second-order dynamical systems with state-dependent uncertainty is developed. The proposed framework guarantees global asymptotic stability of the closed-loop system states associated with the plant dynamics without requiring any knowledge of the system nonlinearities other than the assumption that they are continuous and lower bounded. Generalizations to the case where the system nonlinearities are unbounded are also considered. In the special case of matrix second-order systems with polynomial nonlinearities with unknown coefficients and unknown order, we provide a universal adaptive controller that guarantees closed-loop stability of the plant states.

In this paper, we address the analysis and state-feedback synthesis problems for linear parameter-varying (LPV) systems with parameter-varying time delays. It is assumed that the state-space data and the time delays depend on parameters that are measurable in real-time and vary in a compact set with bounded variation rates. We explore the delay-dependent stability and the induced L 2 norm performance of these systems using parameter-dependent Lyapunov functions. In addition, the state-feedback control synthesis problem is examined when a variable state delay is present. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved via efficient interior-point algorithms.