Simulation verification techniques study

Results are summarized of the simulation verification techniques study which consisted of two tasks: to develop techniques for simulator hardware checkout and to develop techniques for simulation performance verification (validation). The hardware verification task involved definition of simulation hardware (hardware units and integrated simulator configurations), survey of current hardware self-test techniques, and definition of hardware and software techniques for checkout of simulator subsystems. The performance verification task included definition of simulation performance parameters (and critical performance parameters), definition of methods for establishing standards of performance (sources of reference data or validation), and definition of methods for validating performance. Both major tasks included definition of verification software and assessment of verification data base impact. An annotated bibliography of all documents generated during this study is provided

Airborne Advanced Reconfigurable Computer System (ARCS)

A digital computer subsystem fault-tolerant concept was defined, and the potential benefits and costs of such a subsystem were assessed when used as the central element of a new transport's flight control system. The derived advanced reconfigurable computer system (ARCS) is a triple-redundant computer subsystem that automatically reconfigures, under multiple fault conditions, from triplex to duplex to simplex operation, with redundancy recovery if the fault condition is transient. The study included criteria development covering factors at the aircraft's operation level that would influence the design of a fault-tolerant system for commercial airline use. A new reliability analysis tool was developed for evaluating redundant, fault-tolerant system availability and survivability; and a stringent digital system software design methodology was used to achieve design/implementation visibility

Modelling of servo-controlled pneumatic drives: a generalised approach to pneumatic modelling and applications in servo-drive design

The primary objective of this research is to develop a general modelling facility for modular pneumatic servo-drives. The component-oriented approach has been adopted as the modelling technique to provide the flexibility of modelling a wide variety of components and the segmentation of the non-linear system to less complex uncoupled component modules. A significant part of the research work has been devoted to identify a series of component modules of the single axis linear pneumatic servomechanism with standardised linking variables. The mathematical models have been implemented in a simulation software which produces time domain responses for design evaluation purposes. Alternative components for different servomechanism design were modelled as mutually exclusive modules which could be selected for assembly as if they were real physical entities. The philosophy of the approach was validated by tests on prototype servo-drives with matching components. Design analysis could be performed by simulating and comparing the performance of alternative system structures. [Continues.

Motion control and synchronisation of multi-axis drive systems

Motion control and synchronisation of multi-axis drive system

RADAR Based Collision Avoidance for Unmanned Aircraft Systems

Unmanned Aircraft Systems (UAS) have become increasingly prevalent and will represent an increasing percentage of all aviation. These unmanned aircraft are available in a wide range of sizes and capabilities and can be used for a multitude of civilian and military applications. However, as the number of UAS increases so does the risk of mid-air collisions involving unmanned aircraft. This dissertation aims present one possible solution for addressing the mid-air collision problem in addition to increasing the levels of autonomy of UAS beyond waypoint navigation to include preemptive sensor-based collision avoidance. The presented research goes beyond the current state of the art by demonstrating the feasibility and providing an example of a scalable, self-contained, RADAR-based, collision avoidance system. The technology described herein can be made suitable for use on a miniature (Maximum Takeoff Weight \u3c 10kg) UAS platform. This is of paramount importance as the miniature UAS field has the lowest barriers to entry (acquisition and operating costs) and consequently represents the most rapidly increasing class of UAS

Design and control of components-based integrated servo pneumatic drives

On-off traditional pneumatic drives are most widely used in industry offering low-cost, simple but flexible mechanical operation and relatively high power to weight ratio. For a period of decade from mid 1980's to 1990's, some initiatives were made to develop servo pneumatic drives for most sophisticated applications, employing purpose-designed control valves for pneumatic drives and low friction cylinders. However, it is found that the high cost and complex installation have discouraged the manufacturer from applying servo pneumatic drives to industrial usage, making them less favourable in comparison to their electric counterpart. This research aims to develop low-cost servo pneumatic drives which are capable of point-to-point positioning tasks, suitable for applications requiring intermediate performance characteristics. In achieving this objective, a strategy that involves the use of traditional on-off valve, simple control algorithm and distributed field-bus control networks has been adopted, namely, the design and control of Components-based Integrated Pneumatic Drives (CIPDs). Firstly, a new pneumatic actuator servo motion control strategy has been developed. With the new motion control strategy, the processes of positioning a payload can be achieved by opening the control valve only once. Hence, lowspeed on-off pneumatic control valves can be employed in keeping the cost low, a key attraction for employing pneumatic drives. The new servo motion control strategy also provides a way of controlling the load motion speed mechanically. Meanwhile, a new PD-based three-state closed-loop control algorithm also has been developed for the new control scheme. This control algorithm provides a way of adapting traditional PID (Proportional Integral Derivative) control theories for regulating pneumatic drives. Moreover, a deceleration control strategy has been developed so that both high-speed and accurate positioning control can be realised with low cost pneumatic drives. Secondly, the effects of system parameters on the transient response are studied. In assisting the analysis, a second order model is developed to encapsulate the velocity response characteristics of pneumatic drives to a step input signal. Stability analyses for both open loop and closed-loop control have also been carried out for the CIPDs with the newly developed motion control strategy. Thirdly, a distributed control strategy employing Lon Works has been devised and implemented, offering desirable attributes, high re-configurability, low cost and easy in installation and maintenance, etc to keep with the traditional strength for using pneumatic drives. By applying this technology, the CIPDs become standard components in "real" and "virtual" design environments. A remote service strategy for CIPDs using TCP/IP communication protocol has also been developed. Subsequently a range of experimental verifications has been carried out in the research. The experimental study of high-speed motion control indicates that the deceleration control strategy developed in the research can be an effective method in improving the behaviour of high speed CIPDs. The verification of open loop system behaviour of CIPDs shows that the model derived is largely indicative of the likely behaviour for the system considered, and the steady state velocity can be estimated using the Velocity Gain Kv. The evaluation made on a pneumatically driven pick-and-place machine has also confirmed that the system setup, including wiring, tuning, and system reconfiguration can be achieved in relative ease. This pilot study reveals the potential for employing CIPDs in building highly flexible cost effective manufacturing machines. It can thus be concluded that this research has developed successfully a new dimension and knowledge in both theoretical and practical terms in building low-cost servo pneumatic drives, which are capable of point-to-point positioning through employing traditional on-off pneumatic valves and actuators and through their integration with distributed control technology (LonWorks) by adopting a component-based design paradigm

Design study for LANDSAT-D attitude control system

The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse

Aspects of an open architecture robot controller and its integration with a stereo vision sensor.

The work presented in this thesis attempts to improve the performance of industrial robot systems in a flexible manufacturing environment by addressing a number of issues related to external sensory feedback and sensor integration, robot kinematic positioning accuracy, and robot dynamic control performance. To provide a powerful control algorithm environment and the support for external sensor integration, a transputer based open architecture robot controller is developed. It features high computational power, user accessibility at various robot control levels and external sensor integration capability. Additionally, an on-line trajectory adaptation scheme is devised and implemented in the open architecture robot controller, enabling a real-time trajectory alteration of robot motion to be achieved in response to external sensory feedback. An in depth discussion is presented on integrating a stereo vision sensor with the robot controller to perform external sensor guided robot operations. Key issues for such a vision based robot system are precise synchronisation between the vision system and the robot controller, and correct target position prediction to counteract the inherent time delay in image processing. These were successfully addressed in a demonstrator system based on a Puma robot. Efforts have also been made to improve the Puma robot kinematic and dynamic performance. A simple, effective, on-line algorithm is developed for solving the inverse kinematics problem of a calibrated industrial robot to improve robot positioning accuracy. On the dynamic control aspect, a robust adaptive robot tracking control algorithm is derived that has an improved performance compared to a conventional PID controller as well as exhibiting relatively modest computational complexity. Experiments have been carried out to validate the open architecture robot controller and demonstrate the performance of the inverse kinematics algorithm, the adaptive servo control algorithm, and the on-line trajectory generation. By integrating the open architecture robot controller with a stereo vision sensor system, robot visual guidance has been achieved with experimental results showing that the integrated system is capable of detecting, tracking and intercepting random objects moving in 3D trajectory at a velocity up to 40mm/s

Modeling, Simulation and Control of Very Flexible Unmanned Aerial Vehicle

This dissertation presents research on modeling, simulation and control of very flexible aircraft. This work includes theoretical and numerical developments, as well as experimental validations. On the theoretical front, new kinematic equations for modeling sensors are derived. This formulation uses geometrically nonlinear strain-based finite elements developed as part of University of Michigan Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). Numerical linearizations of both the flexible vehicle and the sensor measurements are developed, allowing a linear time invariant model to be extracted for control analysis and design. Two different algorithms to perform sensor fusion from different sensor sources to extract elastic deformation are investigated. Nonlinear least square method uses geometry and nonlinear beam strain-displacement kinematics to reconstruct the wing shape. Detailed information such as material properties or loading conditions are not required. The second method is the Kalman filter, implemented in a multi-rate form. This method requires a dynamical system representation to be available. However, it is more robust to noise corruption in sensor measurements. In order to control maneuver loads, Model Predictive Control is applied to maneuver load alleviation of a representative very flexible aircraft (X-HALE). Numerical studies are performed in UM/NAST for pitch up and roll maneuvers. Both control and state constraints are successfully enforced, while reference commands are still being tracked. MPC execution is also timed and current implementation is capable of almost real-time operation. On the experimental front, two aeroelastic testbed vehicles (ATV-6B and RRV-6B) are instrumented with sensors. On ATV-6B, an extensive set of sensors measuring structural, flight dynamic, and aerodynamic information are integrated on-board. A novel stereo-vision measurement system mounted on the body center looking towards the wing tip measures wing deformation. High brightness LEDs are used as target markers for easy detection and to allow each view to be captured with fast camera shutter speed. Experimental benchmarks are conducted to verify the accuracy of this methodology. RRV-6B flight test results are presented. System identification is applied to the experimental data to generate a SISO description of the flexible aircraft. System identification results indicate that the UM/NAST X-HALE model requires some tuning to match observed dynamics. However, the general trends predicted by the numerical model are in agreement with flight test results. Finally, using this identified plant, a stability augmentation autopilot is designed and flight tested. This augmentation autopilot utilizes a cascaded two-loop proportional integral control design, with the inner loop regulating angular rates and outer loop regulating attitude. Each of the three axes is assumed to be decoupled and designed using SISO methodology. This stabilization system demonstrates significant improvements in the RRV-6B handling qualities. This dissertation ends with a summary of the results and conclusions, and its main contribution to the field. Suggestions for future work are also presented.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144019/1/pziyang_1.pd

Performance Analysis Of Non-Linear Adaptive Control Laws Using Hardware in the Loop of an Unmanned Aerial System

In practical applications, an Unmanned Aerial System\u27s (UAS) baseline performance is dictated by how well it can follow a given trajectory with limited stress on the actuators. However, these can be insufficient performance metrics when the UAS is allowed to adapt to an unpredicted external influence such as turbulence or actuation failure, while maintaining a satisfactory baseline performance. In this thesis, different control laws based on the formation flight geometry problem, nonlinear dynamic inversion and an artificial immune system adaptive mechanism , are implemented in hardware-in-the-loop as a precursor for in-flight testing. These controllers are compared based on three performance metrics: trajectory following, control activity and computer task execution time. The controllers chosen for comparison are: Basic Proportional-Integral-Derivative (PID), Outer loop Non-Linear Dynamic Inversion (NLDI), Extended NLDI, and the previous three controllers augmented with an AIS for a total of six controllers. The Extended NLDI augmented with the AIS outperformed all of the other algorithms under falure conditions on a global scale