Static Position Error Research Articles

Complete Online Algorithm for Air Data System Calibration

Air data systems require costly calibration of their static pressure sensors to characterize errors caused by the act of flying. Altitude-based methods for measuring these so-called static position errors, such as the tower flyby, produce accurate results but require an elaborate flyby site, multiple experiments to capture the relationship between error and airspeed, and are limited to subsonic airspeeds due to inherent hazards to land-based and aircraft structures from low-altitude supersonic flight. Airspeed-based methods using the Global Positioning System (GPS) are generally easier to execute, but they tend to yield less precise results and still require multiple experiments. Additionally, they require temperature probe calibration from external sources. This paper proposes a self-contained online method for complete air data calibration. The proposed method uses a Kalman smoother to fuse GPS altitude and airspeed measurements, aircraft attitude, and air data to produce the full static position error curve as a function of Mach number in a single experiment, with no need for external temperature calibration and with no supersonic limitations. The proposed method is validated using T-38C flight data, and it is shown to reduce cost by 88% while modeling a 42% larger domain when compared to current methods.

Static position errors correction on the satellite optical communication terminal

Static position errors are usually ineluctable during the assembly of a satellite optical communication terminal, which will lead to pointing errors and make it difficult to establish an optical communication link. The model resulting from static position errors of satellite optical communication terminal has been efficiently established through the transformation matrix between the coordinate system of an optical terminal and satellite. Hence, the static position errors for a satellite optical communication terminal can be well predicted. Our results show that the pointing error can be reduced from thousands of microradians to hundreds of microradians, which has been also validated in orbit to greatly improve the quality of optical communication link of HY-2 satellite.

Research on Feed-Forward Controller for Electronic Throttle Control of GDI Engine Based on Nonlinear Model

The nonlinear Hammerstein model was designed. The model was used to compensate the dynamic behavior of an electronic throttle body at different operating conditions. It consisted of a static nonlinear function and a dynamic linear function. The static nonlinear function was used to representing the coulomb friction and limp-home return springs and the dynamic linear function was used to representing dynamic piecewise-linear characteristic. An observer model, known as kalman was used for the on-line throttle position and angular velocity estimation. The control strategy was designed which combined the feed-forward control based on Hammerstein model and feedback control based on proportional-integral-derivative (PID) controller. The control structure has the quick response characteristic of the feed-forward control and disturb compensation characteristic of the feedback control. The experimental results revealed that the dynamic position control delay less than 100ms, the static position error less than 0.5o and the controller satisfied requirement of GDI for precise in-charge control.

Serial manipulator functional calibration for in vitro biomechanical testing

Serial manipulators are often used in biomechanical testing of human joints because they are precise, repeatable instruments that can create interesting loading scenarios. Unfortunately, commercial serial manipulators often do not have acceptable global positional accuracy due to manufacturing tolerances, assembly errors, and other mechanical imperfections. Numerous calibration methods have been reported which calibrate geometric and non-geometric parameters to reduce static position errors under constant loading conditions. However, the manipulator's global accuracy during continuous motion with time-varying external loading conditions is often not addressed but is necessary for joint biomechanical testing. Using the Mitsubishi PA10-6CE as a case study, a novel functional calibration procedure was developed that performs both static and dynamic calibration. The calibration uses optimization techniques to populate a 34-parameter model that accounts for the robot's geometric and non-geometric parameters and significantly reduces the mean/peak static and dynamic position errors to 0.368/0.67mm and 0.353/0.81mm, respectively, while externally loaded.

Control of position and movement is simplified by combined muscle spindle and Golgi tendon organ feedback

Whereas muscle spindles play a prominent role in current theories of human motor control, Golgi tendon organs (GTO) and their associated tendons are often neglected. This is surprising since there is ample evidence that both tendons and GTOs contribute importantly to neuromusculoskeletal dynamics. Using detailed musculoskeletal models, we provide evidence that simple feedback using muscle spindles alone results in very poor control of joint position and movement since muscle spindles cannot sense changes in tendon length that occur with changes in muscle force. We propose that a combination of spindle and GTO afferents can provide an estimate of muscle-tendon complex length, which can be effectively used for low-level feedback during both postural and movement tasks. The feasibility of the proposed scheme was tested using detailed musculoskeletal models of the human arm. Responses to transient and static perturbations were simulated using a 1-degree-of-freedom (DOF) model of the arm and showed that the combined feedback enabled the system to respond faster, reach steady state faster, and achieve smaller static position errors. Finally, we incorporated the proposed scheme in an optimally controlled 2-DOF model of the arm for fast point-to-point shoulder and elbow movements. Simulations showed that the proposed feedback could be easily incorporated in the optimal control framework without complicating the computation of the optimal control solution, yet greatly enhancing the system's response to perturbations. The theoretical analyses in this study might furthermore provide insight about the strong physiological couplings found between muscle spindle and GTO afferents in the human nervous system.

A Model-Free Fine Position Control Method Using the Base-Sensor: With Application to a Hydraulic Manipulator

Manipulators are often required to perform small amplitude, slow motions with very high precision. For hydraulic manipulators these fine motions are difficult to execute due to high nonlinear joint friction found in these systems. Poor tracking, stick-slip behavior, and large static position errors often occur. Current methods proposed to improve the performance of hydraulic manipulators require complex modeling and identification and often produce marginal results. Here, a control scheme based on feedback from a base-mounted force/torque sensor is presented. The theoretical background for the method is presented, and an easy to implement simplified form is developed, based on quasi-static equations. Experimental results for a Schilling Titan II industrial hydraulic manipulator performing fine-motion tasks under the simplified control algorithm are presented. It is shown that performance is significantly improved over traditional control methods. It is also shown that the control scheme is robust to changes in payload.

Velocity prediction in corrective saccades during smooth-pursuit eye movements in monkey

It has been noted in a variety of studies in both humans and monkeys that saccades made during smooth pursuit eye movements are usually quite accurate. Since saccades are known to be planned on the basis of neuronal information existing at some interval of time before the actual onset of the movement, it is generally accepted that some sort of prediction or use of visual motion velocity is combined with static position error in the execution of these saccades to moving targets. However, statistical treatment of this response in humans has provided evidence for alternative mechanisms, including a strategy of saccading ahead in the direction of target motion without any incorporation of actual speed information about target motion in the response. We reinvestigated this question quantitatively in the monkey on a large data base of saccades. We found evidence that supports the hypothesis that information about target speed per se is used in this species in the production of saccades to moving targets. Multiple linear regression analysis supported the hypothesis that information about the position error and the target velocity that exists at about 100 ms prior to the saccade onset are both required to provide a statistical explanation of saccade size during pursuit eye movements under the conditions of our experiments.