The Effect of Sensor Spacing on the Calculation of Angular Acceleration of Vehicles

Vehicle vibration presents challenges to a packaged product that are inevitable in any distribution environment. Typically products are tested in only a single, vertical axis, however researchers have shown that there is energy in all six axes of motion. In past work, for a packaging application, the response of a vehicle or product has not been recorded in all six axes. In the current standards, classification of motion and potential multi-axis testing methods are discussed. In this work, we study the recording methods of the six degree of freedom (6 DOF) motion of a transport vehicle. A co-planar sensor array, three tri-axial linear accelerometers, and three angular rate sensors, are mounted in a L shape to calculate the rotational accelerations that occur in the back of a vehicle. Missing from prior work is a scientific study designed to determine the minimum sensor spacing necessary to accurately capture the yaw, pitch, and roll of transport vehicles. A sensitivity study is conducted to determine the effect of the misplacement and misorientation of sensors on the angular acceleration calculation. A laboratory study is used to determine the sensor spacing mounting error that begins to accumulate in the angular acceleration calculation in response to a sinusoidal input. A field study is conducted to calculate the rotational motions of a vehicle on a rough road. It is found that a mounting fixture is valuable in assuring the necessary sensor placement accuracy needed to accurately determine angular accelerations of a truck. Additionally, laboratory and field analysis show that as the sensor spacing location approaches the origin sensor, angular acceleration calculation error increases due to a loss in sensor signal distinctiveness. Sensors can be mounted closer than 76.20 cm and can be mounted as close as 25.40 cm without accumulating significant error

INFLUENCES ANALYSIS OF CONFIGURATIONS ON THE PERFORMANCE OF PARALLEL TYPE SIX-AXIS ACCELEROMETERS

The development of parallel type six-axis accelerometers was hindered for their complicated forward kinematics and dynamics algorithms which make it difficult to decouple the six acceleration components timely, accurately and stably. This paper applies four parallel configurations with 6-DOF and a closed-form solution of the forward kinematics to six-axis accelerometers as the elastic bodies, where the piezoelectric ceramics act as the sensitive elements and play the role of prismatic pairs. An efficient decoupling algorithm was derived to calculate the six acceleration components completely by the use of Kane’s dynamics method in configuration space. Considering the differences in sensing properties of the four six-axis accelerometers, a quantitative comparison was conducted to reveal the configurations’ direct influences on some static characteristics, including accuracy, efficiency, sensitivity, isotropy, and working frequency range, which makes a theoretical foundation for the subsequent design of a reconfigurable prototype

INFLUENCES ANALYSIS OF CONFIGURATIONS ON THE PERFORMANCE OF PARALLEL TYPE SIX-AXIS ACCELEROMETERS

The development of parallel type six-axis accelerometers was hindered for their complicated forward kinematics and dynamics algorithms which make it difficult to decouple the six acceleration components timely, accurately and stably. This paper applies four parallel configurations with 6-DOF and a closed-form solution of the forward kinematics to six-axis accelerometers as the elastic bodies, where the piezoelectric ceramics act as the sensitive elements and play the role of prismatic pairs. An efficient decoupling algorithm was derived to calculate the six acceleration components completely by the use of Kane’s dynamics method in configuration space. Considering the differences in sensing properties of the four six-axis accelerometers, a quantitative comparison was conducted to reveal the configurations’ direct influences on some static characteristics, including accuracy, efficiency, sensitivity, isotropy, and working frequency range, which makes a theoretical foundation for the subsequent design of a reconfigurable prototype

Best Axes Composition Extended: Multiple Gyroscopes and Accelerometers Data Fusion to Reduce Systematic Error

Multiple rigidly attached Inertial Measurement Unit (IMU) sensors provide a richer flow of data compared to a single IMU. State-of-the-art methods follow a probabilistic model of IMU measurements based on the random nature of errors combined under a Bayesian framework. However, affordable low-grade IMUs, in addition, suffer from systematic errors due to their imperfections not covered by their corresponding probabilistic model. In this paper, we propose a method, the Best Axes Composition (BAC) of combining Multiple IMU (MIMU) sensors data for accurate 3D-pose estimation that takes into account both random and systematic errors by dynamically choosing the best IMU axes from the set of all available axes. We evaluate our approach on our MIMU visual-inertial sensor and compare the performance of the method with a purely probabilistic state-of-the-art approach of MIMU data fusion. We show that BAC outperforms the latter and achieves up to 20% accuracy improvement for both orientation and position estimation in open loop, but needs proper treatment to keep the obtained gain.Comment: Accepted to Robotics and Autonomous Systems journal. arXiv admin note: substantial text overlap with arXiv:2107.0263

Compensation for Inertial and Gravity Effects in a Moving Force Platform

Force plates for human movement analysis provide accurate measurements when mounted rigidly on an inertial reference frame. Large measurement errors occur, however, when the force plate is accelerated, or tilted relative to gravity. This prohibits the use of force plates in human perturbation studies with controlled surface movements, or in conditions where the foundation is moving or not sufficiently rigid. Here we present a linear model to predict the inertial and gravitational artifacts using accelerometer signals. The model is first calibrated with data collected from random movements of the unloaded system and then used to compensate for the errors in another trial. The method was tested experimentally on an instrumented force treadmill capable of dynamic mediolateral translation and sagittal pitch. The compensation was evaluated in five experimental conditions, including platform motions induced by actuators, by motor vibration, and by human ground reaction forces. In the test that included all sources of platform motion, the root-mean-square (RMS) errors were 39.0 N and 15.3 N m in force and moment, before compensation, and 1.6 N and 1.1 N m, after compensation. A sensitivity analysis was performed to determine the effect on estimating joint moments during human gait. Joint moment errors in hip, knee, and ankle were initially 53.80 N m, 32.69 N m, and 19.10 N m, and reduced to 1.67 N m, 1.37 N m, and 1.13 N m with our method. It was concluded that the compensation method can reduce the inertial and gravitational artifacts to an acceptable level for human gait analysis

Flight Control and Hardware Design of Multi-Rotor Systems

This thesis overviews crucial concepts involved in achieving quadcopter flight such as orientation estimation and control system implementation. This thesis also presents researchers with comprehensive hardware and software specifications for a quadcopter system. The primary application for this system would be for research with regards to the implementation of advance control techniques as well as data acquisition. Key constructs of this system include hardware software specifications for a flight controller, the radio system, and the sensorless brushless motor controllers. Firstly, the thesis starts by developing a reference frame and a mathematical model for the quadcotper system. Next, flight orientation estimation is determined through an assortment of MEMS sensors such as an accelerometer, gyroscope, and magnetometer. Each sensor will be individually addressed as to its strengths and weaknesses with regards to orientation estimation. An algorithm will then be proposed for the data fusion of these various sensors. This fused data will then be fed into a control system that will efficiently stabilize the quadcopter. Finally, this thesis will overview methods of integrating lidar data directly into the quadcopter\u27s control system. Real-world lidar data is used and a computational geometry algorithm, ICL, is employed to translate the point cloud data into relevant control parameters

Proceedings of an ESA-NASA Workshop on a Joint Solid Earth Program

The NASA geodynamics program; spaceborne magnetometry; spaceborne gravity gradiometry (characterizing the data type); terrestrial gravity data and comparisons with satellite data; GRADIO three-axis electrostatic accelerometers; gradiometer accommodation on board a drag-free satellite; gradiometer mission spectral analysis and simulation studies; and an opto-electronic accelerometer system were discussed

Measuring the acceleration of a rigid body

Two methods to measure the six-degree-of-freedom acceleration of a point on a rigid body are presented. The first, referred to as the periphery scheme, makes use of three clusters of accelerometers mounted orthogonal to each other and coincident with the axes of the point. One of the clusters consists of the three accelerometers attached to a cube-shaped triaxial angular rate sensor (ARS). The second method, called the compact cube scheme, uses a single 3-accelerometer/ARS cluster that may be mounted anywhere on the rigid body. During impact tests with an instrumented rigid body, both methods produced measurements that were highly correlated near the time of peak acceleration. Whereas the compact cube scheme was more economical and easier to implement, the periphery scheme produced results that were less disrupted by instrument signal errors and noisy environments