Acceleration Feedback via an algebraic state estimation method

International audienceIn many mechanical systems, only accelerations are available for feedback purposes. For example, certain aerospace, positioning systems and force-position controllers in robotic systems, use accelerometers as the only sensing device. This paper presents initial steps towards an algebraic approach for the state estimation based feedback control problem in systems where the highest order derivative of the controlled variable is available. An illustrative case is presented dealing with the trajectory tracking problem for a second order position system on which only the acceleration is available for measurement. Based on an algebraic approach, an on-line algebraic estimator is developed for the unmeasured position and velocity variables. The obtained expressions depend solely on iterated integrals of the measured acceleration output and of the control input. The approach is robust to noisy measurement and it has the advantage to provide fast, on-line, non-asymptotic state estimations in the form of formula requiring only the input and the output of the system. Based on these estimations, a linear feedback control law including estimated position error integrals is designed illustrating the possibilities of acceleration feedback via algebraic state estimation

WALLSY: The UWB and SmartMesh IP enabled Wireless Ad-hoc Low-power Localization SYstem

This paper follows the implementation of a proofof-concept localization system for GNSS-denied environments. WALLSY (Wireless Ad-hoc Low-power Localization SYstem) is a portable and modular Ultra Wide-Band (UWB) and Smart Mesh IP (SMIP) hybrid. WALLSY uses UWB two way ranging (TWR) to measure distances, which are then sent via the lowpower SMIP backbone network to a central hub for calculating coordinates of tracked objects. The system is highly flexible and requires no external infrastructure or prior knowledge of the installation site. It uses a completely nomadic topology and delivers high localization accuracy with all modules being battery powered. It achieves this by using a custom time-slotting protocol which maximizes deep-sleep mode for UWB. Battery life can be further improved by activating inertial measurement unit (IMU) filtering. Visualization of tracked objects and system reconfiguration can be executed on-the-fly and are both accessible to end users through a simple graphical user interface (GUI). Results demonstrate that WALLSY can achieve more than ten times longer battery lifetime compared to competing solutions (localizing every 30 seconds). It provides 3D coordinates with an average spatial error of 60.5cm and an average standard deviation of 15cm. The system also provides support for up to 20 tags

Algebraic methods for state estimation of unmanned aerial vehicles by using accelerometer

U ovom radu razmatrana je primjena algebarskih metoda estimacije stanja autonomne letjelice primjenom akcelerometra s ciljem sinteze regulacijskog sustava letjelice. Algebarske metode omogućuju robusnu identifikaciju parametara i estimaciju stanja sustava u realnom vremenu te predstavljaju potencijalnu alternativu konvencionalnom asimptotskom pristupu estimaciji varijabli stanja sustava. Algebarske metode estimacije primjenjene su na linearizirani model potpuno upravljive letjelice sa šest zakrenutih rotora, koji omogućuje potpuno decentralizirano upravljanje po svakom stupnju slobode gibanja letjelice. Pretpostavka je da je početna pozicija letjelice u ishodištu inercijalnog sustava te da postoji nepoznata konstantna pogreška mjerenja akceleracije. Korištena je konvencionalna algebarska metoda te metoda frekvencijskog pomaka za dobivanje izraza za algebarsku estimaciju drifta akcelerometra dok je za usporedbu s asimptotskom metodom korišten robusni kompenzator drifta akcelerometra.This thesis discusses application of algebraic estimation methods of autonomous aircraft by using accelerometer with the aim of forming the aircraft control system. Algebraic methods enable robust parameter identification and real-time system estimation which represent a potential alternative to a conventional asymptotic approach to system state estimation. Algebraic estimation methods were applied to a linearized model of a fully actuated aircraft with six passively tiled rotors, which allows for a fully decentralized control of each aircraft degree of freedom. The assumption is that the initial position of the aircraft is at the origin of the inertial system and that tere is an unkown constant error in acceleration measurement. A conventional algebraic method and a frequency shift method were used to obtain expressions for algebraic accelerometer drift estimation, while for comparison with the asymptotic method a robust compensator of accelerometer drift was used

Algebarske metode estimacije stanja autonomne letjelice primjenom akcelerometra

U ovom radu razmatrana je primjena algebarskih metoda estimacije stanja autonomne letjelice primjenom akcelerometra s ciljem sinteze regulacijskog sustava letjelice. Algebarske metode omogućuju robusnu identifikaciju parametara i estimaciju stanja sustava u realnom vremenu te predstavljaju potencijalnu alternativu konvencionalnom asimptotskom pristupu estimaciji varijabli stanja sustava. Algebarske metode estimacije primjenjene su na linearizirani model potpuno upravljive letjelice sa šest zakrenutih rotora, koji omogućuje potpuno decentralizirano upravljanje po svakom stupnju slobode gibanja letjelice. Pretpostavka je da je početna pozicija letjelice u ishodištu inercijalnog sustava te da postoji nepoznata konstantna pogreška mjerenja akceleracije. Korištena je konvencionalna algebarska metoda te metoda frekvencijskog pomaka za dobivanje izraza za algebarsku estimaciju drifta akcelerometra dok je za usporedbu s asimptotskom metodom korišten robusni kompenzator drifta akcelerometra

Acceleration Feedback via an algebraic state estimation method

International audienceIn many mechanical systems, only accelerations are available for feedback purposes. For example, certain aerospace, positioning systems and force-position controllers in robotic systems, use accelerometers as the only sensing device. This paper presents initial steps towards an algebraic approach for the state estimation based feedback control problem in systems where the highest order derivative of the controlled variable is available. An illustrative case is presented dealing with the trajectory tracking problem for a second order position system on which only the acceleration is available for measurement. Based on an algebraic approach, an on-line algebraic estimator is developed for the unmeasured position and velocity variables. The obtained expressions depend solely on iterated integrals of the measured acceleration output and of the control input. The approach is robust to noisy measurement and it has the advantage to provide fast, on-line, non-asymptotic state estimations in the form of formula requiring only the input and the output of the system. Based on these estimations, a linear feedback control law including estimated position error integrals is designed illustrating the possibilities of acceleration feedback via algebraic state estimation