This thesis is focused on individual wheel actuators in road vehicles intended for vehicle motion control. Particular attention is paid to electro-mechanical actuators and how they can contribute to improving vehicle dynamics and safety. The employment of individual wheel actuators at the vehicle's four corner results in a large degree of over-actuation. Over-actuation has a potential of exploiting the vehicle's force constraints at a high level and of controlling the vehicle more freely. One important reason for using over-actuated vehicles is their capability to assist the driver to experience the vehicle as desired. This thesis demonstrates that critical situations close to the limits can be handled more efficiently by over-actuation. To maximise the vehicle performance, all the available actuators are systematically exploited within their force constraints.  Therefore, force constraints for the individually controlled wheel are formulated, along with important restrictions that follow as soon as a reduction in the degrees of freedom of the wheel occurs. Particular focus is directed at non-convex force constraints arising from combined tyre slip characteristics. To evaluate the differently actuated vehicles, constrained control allocation is employed to control the vehicle. The allocation problem is formulated as an optimisation problem, which is solved by non-linear programming. To emulate realistic safety critical scenarios, highly over-actuated vehicles are controlled and evaluated by the use of a driver model and a validated complex strongly non-linear vehicle model. it is shown that, owing to the actuator redundancy, over-actuated vehicles possess an inherent capacity to handle actuator faults, with less need for extra hardware or case-specific fault-handling strategies. / QC 20100722

The capacity of humankind to mimic fish-like locomotion for engineering applications depends mainly on the availability of suitable actuators. Researchers have recently focused on developing robotic fish using smart materials, particularly Ionic Polymer-Metal Composites (IPMCs), as a compliant, noise-free, and scalable alternative to conventional motor-based propulsion systems. In this thesis, we investigate fish-like self propulsion using flexible bimorphs made of Macro-Fiber Composite (MFC) piezoelectric laminates. Similar to IPMCs, MFCs also exhibit high efficiency in size, energy consumption, and noise reduction. In addition, MFCs offer large dynamic forces in bending actuation, strong electromechanical coupling as well as both low-frequency and high-frequency performance capabilities. The experimental component of the presented work focuses on the characterization of an MFC bimorph propulsor for thrust generation in a quiescent fluid as well as the development of a preliminary robotic fish prototype incorporating a microcontroller and a printed-circuit-board (PCB) amplifier to generate high actuation voltage for battery-powered free locomotion. From the theoretical standpoint, a reliable modeling framework that couples the actuator dynamics, hydroelasticity, and fish locomotion theory is essential to both design and control of robotic fish. Therefore, a distributed-parameter electroelastic model with fluid effects and actuator dynamics is coupled with the elongated body theory. Both in-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated body theory to predict the thrust output. Experiments are conducted to validate the electrohydroelastic modeling approach employed in this work and to characterize the performance of an MFC bimorph propulsor. Finally, a wireless battery-powered preliminary robotic fish prototype is developed and tested in free locomotion at different frequency and voltage levels.

RF/microwave tunable filters are widely employed in radar systems, measurement instruments, and communication systems. By using tunable filters, the frequency bandwidth is utilized effectively and the system cost and complexity is reduced. In the literature, various tuning techniques have been developed to construct tunable filters. Mechanical tuning, magnetic tuning, and electrical tuning are the most common. In terms of quality factor, power handling capability, and linearity, mechanical tuning is superior to the other two tuning techniques. Unfortunately, due to their bulky size, heavy weight, and low tuning speed, mechanically tunable filters have limited applications. MicroElectroMechanical Systems (MEMS) technology has the potential to produce highly miniaturized tunable filters; however, most of the MEMS tunable filters reported so far have a relatively low quality factor. The objective of the research described in this thesis is to investigate the feasibility of using MEMS technology to develop tunable filters with a high quality factor. The integration of MEMS tuning elements with a wide range of filter configurations is explored, from micromachined filters to traditional dielectric resonator filters, from planar filters to cavity filters. Both hybrid integration and monolithic integration approaches are carried out. To achieve tunability, MEMS tuning elements are embedded within RF and microwave filters. Tuning is accomplished by disturbing the electromagnetic fields of resonators with nearby MEMS tuning elements, which in turn change the resonant frequency of the resonators. First, the proposed tuning concept is experimentally demonstrated by integrating a surface micromachined planar filter with MEMS thermal actuators as the tuning elements. Then, a novel micromachined ridge waveguide filter embedded with similar MEMS tuning elements is proposed and constructed by using the EFAB^{TM} micromachining technique. A power handling analysis is performed for the newly devised 3D micromachined filter, and potential failure mechanisms such as air breakdown are identified. For the first time, a tunable dielectric resonator bandpass filter, incorporating vertical long-throw MEMS thermal actuators as tuning elements, is developed to achieve a wide tuning range, high quality factor, and large power handling capability. Several prototype tunable filter units are fabricated and tested. The experimental results reveal that the tunable filters maintain a relatively high quality factor value over a wide tuning range. In addition to the hybrid integration approach, a monolithic integration approach is investigated. A novel surface micromachining process is developed to allow monolithic integration of MEMS tuning elements into micromachined filters. Due to a stress mismatch, MEMS actuators fabricated by this process obtain a vertical deflection of several hundred microns, resulting in a wide tuning range. Various latching mechanisms are created, based on the micromachining processes that are used to fabricate the MEMS tuning elements. These out-of-plane latching mechanisms with multi-stable states have the potential to be adopted not only for tunable filter applications but also for switches and phase shifters.

Shape memory alloys (SMAs) are metallic materials, which have two main stable crystalline phases: austenite, a high temperature phase and martensite, a low temperature phase. Austenite and martensite each have unique physical and mechanical properties, and transformation between these phases enables two effects known as the shape memory effect (SME) and superelasticity. When a material that displays the SME is plastically deformed at low temperature, a heat input will cause the SMA to return to its original shape before the deformation. At higher temperatures, the material displays an effect called superelasticity, where strains of up to 10% are recoverable. These characteristics of SMA allow for significant amounts of strain recovery, and enable the design of SMA actuators. The temperature in an SMA actuator is generally controlled by resistive heating, also know as joule heating, and the strain recovery capabilities are used to do work on a load, thereby creating an electro-mechanical actuator. SMA actuators have attractive properties such as high energy density, smooth and silent actuation, reduced part counts compared to traditional alternatives, and scalability down to the micromechanical level. The phase transformation in SMA actuators, however, is highly non-linear. Therefore, the use of SMA as actuators, for example in positioning systems, benefits from the development of good models to predict and control the materials. The goals of this work are to develop a model suitable for real-time implementation, and that reproduces the observed behaviour of SMA actuators. The model is then inverted and used to develop a model-based controller, used in conjunction with traditional PID control to improve the precision and robustness of SMA actuators. The modelling portion of this work consists of the development of a phenomenological SMA model. The forward model is split into three blocks: a heating block, a phase kinetics block and a mechanical block. Since joule heating is commonly used in SMA actuators to bring about an increase in temperature, the heating block presents equations to convert a current input into the temperature of the wire. The phase kinetics block equations convert the calculated temperature and applied stress to the fraction of martensite present in the SMA. Finally, the mechanical model calculates the strain in the material from the martensite fraction and the applied stress. Once the model equations are presented, experimental verification tests are shown to compare physical SMA behaviour with that predicted by the model. Each of the blocks of the forward model are then inverted in order to be used as a feedforward linearizing controller. The control section of this thesis deals with the response of two common types of SMA actuators: a constant force SMA actuator and a spring-biased SMA actuator. The response of the system to step and sinusoidal signals with period of 5 seconds is investigated using two types of controllers: a traditional PI controller and the inverse-model controller in feedforward with a PI controller in feedback. Additionally, the robustness of the system is investigated through the response of the system to transient and sinusoidal stress disturbances. The disturbance rejection is investigated on a constant force actuator both with and without the presence of a force sensor.

RF/microwave tunable filters are widely employed in radar systems, measurement instruments, and communication systems. By using tunable filters, the frequency bandwidth is utilized effectively and the system cost and complexity is reduced. In the literature, various tuning techniques have been developed to construct tunable filters. Mechanical tuning, magnetic tuning, and electrical tuning are the most common. In terms of quality factor, power handling capability, and linearity, mechanical tuning is superior to the other two tuning techniques. Unfortunately, due to their bulky size, heavy weight, and low tuning speed, mechanically tunable filters have limited applications. MicroElectroMechanical Systems (MEMS) technology has the potential to produce highly miniaturized tunable filters; however, most of the MEMS tunable filters reported so far have a relatively low quality factor. The objective of the research described in this thesis is to investigate the feasibility of using MEMS technology to develop tunable filters with a high quality factor. The integration of MEMS tuning elements with a wide range of filter configurations is explored, from micromachined filters to traditional dielectric resonator filters, from planar filters to cavity filters. Both hybrid integration and monolithic integration approaches are carried out. To achieve tunability, MEMS tuning elements are embedded within RF and microwave filters. Tuning is accomplished by disturbing the electromagnetic fields of resonators with nearby MEMS tuning elements, which in turn change the resonant frequency of the resonators. First, the proposed tuning concept is experimentally demonstrated by integrating a surface micromachined planar filter with MEMS thermal actuators as the tuning elements. Then, a novel micromachined ridge waveguide filter embedded with similar MEMS tuning elements is proposed and constructed by using the EFAB^{TM} micromachining technique. A power handling analysis is performed for the newly devised 3D micromachined filter, and potential failure mechanisms such as air breakdown are identified. For the first time, a tunable dielectric resonator bandpass filter, incorporating vertical long-throw MEMS thermal actuators as tuning elements, is developed to achieve a wide tuning range, high quality factor, and large power handling capability. Several prototype tunable filter units are fabricated and tested. The experimental results reveal that the tunable filters maintain a relatively high quality factor value over a wide tuning range. In addition to the hybrid integration approach, a monolithic integration approach is investigated. A novel surface micromachining process is developed to allow monolithic integration of MEMS tuning elements into micromachined filters. Due to a stress mismatch, MEMS actuators fabricated by this process obtain a vertical deflection of several hundred microns, resulting in a wide tuning range. Various latching mechanisms are created, based on the micromachining processes that are used to fabricate the MEMS tuning elements. These out-of-plane latching mechanisms with multi-stable states have the potential to be adopted not only for tunable filter applications but also for switches and phase shifters.

Shape memory alloys (SMAs) are metallic materials, which have two main stable crystalline phases: austenite, a high temperature phase and martensite, a low temperature phase. Austenite and martensite each have unique physical and mechanical properties, and transformation between these phases enables two effects known as the shape memory effect (SME) and superelasticity. When a material that displays the SME is plastically deformed at low temperature, a heat input will cause the SMA to return to its original shape before the deformation. At higher temperatures, the material displays an effect called superelasticity, where strains of up to 10% are recoverable. These characteristics of SMA allow for significant amounts of strain recovery, and enable the design of SMA actuators. The temperature in an SMA actuator is generally controlled by resistive heating, also know as joule heating, and the strain recovery capabilities are used to do work on a load, thereby creating an electro-mechanical actuator. SMA actuators have attractive properties such as high energy density, smooth and silent actuation, reduced part counts compared to traditional alternatives, and scalability down to the micromechanical level. The phase transformation in SMA actuators, however, is highly non-linear. Therefore, the use of SMA as actuators, for example in positioning systems, benefits from the development of good models to predict and control the materials. The goals of this work are to develop a model suitable for real-time implementation, and that reproduces the observed behaviour of SMA actuators. The model is then inverted and used to develop a model-based controller, used in conjunction with traditional PID control to improve the precision and robustness of SMA actuators. The modelling portion of this work consists of the development of a phenomenological SMA model. The forward model is split into three blocks: a heating block, a phase kinetics block and a mechanical block. Since joule heating is commonly used in SMA actuators to bring about an increase in temperature, the heating block presents equations to convert a current input into the temperature of the wire. The phase kinetics block equations convert the calculated temperature and applied stress to the fraction of martensite present in the SMA. Finally, the mechanical model calculates the strain in the material from the martensite fraction and the applied stress. Once the model equations are presented, experimental verification tests are shown to compare physical SMA behaviour with that predicted by the model. Each of the blocks of the forward model are then inverted in order to be used as a feedforward linearizing controller. The control section of this thesis deals with the response of two common types of SMA actuators: a constant force SMA actuator and a spring-biased SMA actuator. The response of the system to step and sinusoidal signals with period of 5 seconds is investigated using two types of controllers: a traditional PI controller and the inverse-model controller in feedforward with a PI controller in feedback. Additionally, the robustness of the system is investigated through the response of the system to transient and sinusoidal stress disturbances. The disturbance rejection is investigated on a constant force actuator both with and without the presence of a force sensor.

This research addresses the ability of dissipative passive actuators to generate control effects on a passive haptic interface. A haptic display is a human-machine interface that constructs a sensation of touch for the human operator. Applications can be found in various industries, space, medicine and construction etc. A dissipative passive haptic display contains passive actuators that can remove energy from the system by resisting motions in the system. The advantage of a dissipative passive haptic display is better safety compared to an active display. Its disadvantage is the limited control ability from the passive actuators. This research starts with the identification of the control ability and limitations of dissipative passive haptic interfaces. The ability is identified as the steerability, the ability to redirect motions of a manipulator. The force generation analysis of each individual actuator is then selected as an approach to evaluate the steerability. Steerability metrics are defined to evaluate the steerability. Even though non-redundant manipulators dont have desired steerability, optimal steering configurations are found for the best operation. Steerability is improved by redundancy in serial or parallel structures. A theorem is developed to evaluate steerability for redundant manipulators. The influence of system dynamics on their steerabilities is discussed. Previously developed haptic interfaces are evaluated based on their steerabilities. Steerability analysis of three-dimensional haptic interfaces is also given to a limited extent as an extension of the two-dimensional cases. Brakes and clutches are the two types of dissipative passive actuators in this research.

The finite element method (FEM) has difficulty solving certain problems where adaptive mesh is needed. Motivated by two engineering problems in live-object handling project, this research focus on a new computational method called the meshless method (MLM). This method is built upon the same theoretical framework as FEM but needs no mesh. Consequently, the computation becomes more stable and the adaptive computational scheme becomes easier to develop. In this research, we investigate practical issues related to the MLM and develop an adaptive algorithm to automatically insert additional nodes and improve computational accuracy. The study has been in the context of the two engineering problems: magnetic field computation and large deformation contact. First, we investigate the effect of two discretization methods (strong-form and weak-form) in MLM for solving linear magnetic field problems. Special techniques for handling the discontinuity boundary condition at material interfaces are proposed in both discretization methods to improve the computational accuracy. Next, we develop an adaptive computational scheme in MLM that is comprised of an error estimation algorithm, a nodal insertion scheme and a numerical integration scheme. As a more general approach, this method can automatically locate the large error region around the material interface and insert nodes accordingly to reduce the error. We further extend the adaptive method to solve nonlinear large deformation contact problems. With the ability to adaptively insert nodes during the computation, the developed method is capable of using fewer nodes for initial computation and thus, effectively improves the computational efficiency. Engineering applications of the developed methods have been demonstrated by two practical engineering problems. In the first problem, the MLM has been utilized to simulate the dynamic response of a non-contact mechanical-magnetic actuator for optimizing the design of the actuator. In the second problem, the contact between the flexible finger and the live poultry product has been analyzed by using MLM. These applications show the developed method can be applied to a broad spectrum of engineering applications where an adaptive mesh is needed.

The performance of a high-power small-scale combustion-based fluidic actuator for high-speed flow control applications is characterized with specific focus on comparisons between premixed and nonpremixed operating modes for the device. Momentary (pulsed) actuation jets are produced by the ignition of a mixture of gaseous fuel and oxidizer within a small (cubic centimeter scale) combustion chamber. The combustion process yields a high pressure burst (1 to 3 ms in duration in the typical configurations) and the ejection of a high-speed exhaust jet. The actuation frequency can be continuously varied by independently controlling the flow rate of the fuel/oxidizer and the spark ignition frequency up to a maximum determined by the operating characteristics of the actuator. The actuator performance is characterized by both its peak thrust and net total impulse, with increases in peak jet momentum often two to three orders of magnitude above the baseline steady jet. Results for operation of the device in both premixed and nonpremixed modes are presented and analyzed, with nonpremixed operation typically yielding higher pressures and greater frequency ranges in the present configurations.

This dissertation presents the development of a novel linear magnetostrictive actuator. The magnetostrictive material used here is Terfenol-D, an alloy of the formula Tb0.3Dy0.7Fe1.92. In response to a traveling magnetic field inside the Terfenol-D element, it moves in the opposite direction with a peristaltic motion. The proposed design offers the flexibility to operate the actuator in various configurations including local and conventional three-phase excitation. The conceptual design of the linear magnetostrictive actuator was performed during which different configurations were analyzed. Finite Element Analysis (FEA) was extensively used for magnetic circuit design and analysis in conceptual design. Eventually one of these designs was chosen based on which detailed design of linear magnetostrictive actuator was carried out. A new force transmission assembly incorporates spring washers to avoid the wear due to the sudden collision of Terfenol-D element with the force transmission assembly. All mechanical parts were then fabricated at the mechanical engineering machine shop. The power electronics to operate the motor in a local three-phase mode was designed and implemented. It was demonstrated that the power consumption can be reduced significantly by operating the magnetostrictive linear actuator in the local excitation mode. A finite-element model of the actuator was developed using ATILA and an empirical model was presented using the data gathered from numerous tests performed on the actuator. The closed-loop control system was implemented using relay control which resulted in an optimal closed-loop performance. The magnetostrictive actuator has demonstrated 410-N load capacity with a travel range of 45 mm, and the maximum speed is 9 mm/min. The maximum power consumption by the motor is 95 W. The sensorless control of the linear magnetostrictive actuator was successfully conducted using two different approaches. First, using a linear-approximation method, we achieved a position estimation capability with ±1 mm error. Then, an adaptive neuro-fuzzy inference system was employed for estimating the position which resulted in a position estimation capability with only a ±0.5 mm error.