Sinteza bezsenzornog upravljanja silom za fleksibilnog robota korištenjem upravljanja omjerom rezonancija temeljenim na metodi koeficijentnog dijagrama

Generally, the flexible robot system can be modeled as the two-mass system which consists of a motor and load connected by a spring. Thus, its elasticity causes resonance in the system. By using the conventional PID controller, this method cannot perform well in this situation. Much research has proceeded with the aim of reducing vibration. A new effective control method, the resonance ratio control, has been introduced as a new way to guarantee the robustness and suppress the oscillation during task executions for a position and force control. In this paper, three techniques are proposed for improving the performance of resonance ratio control. Firstly, a new multi encoder based disturbance observer (MEDOB) is shown to estimate the disturbance force on the load side. The proposed observer is not necessary to identify the nominal spring coefficient. Secondly, coefficient diagram method (CDM) has been applied to calculate a new gain of the force controller. A new resonance ratio gain has been presented as 2.0. Finally, the MEDOB and load side disturbance observer (LDOB) are employed to identify a spring coefficient of flexible robot system. By using the proposed identification method, it is simple to identify the spring coefficient and easy to implement in the real flexible robot system. The effectiveness of the proposed identification method is verified by simulation and experimental results.Općenito, sustav fleksibilnog robota može se modelirati kao dvomaseni sustav koji se sastoji od motora i tereta povezanih oprugom. Rezonancija sustava posljedica je elastičnosti opruge. Korištenje konvencionalnog PID regulatora ne daje zadovoljavajuće performanse u ovoj situaciji. Provedena su mnoga istraživanja s ciljem smanjenja vibracija. Tako je uvedena nova učinkovita metoda upravljanja, upravljanje omjerom rezonancija, kao novi način da se osigura robusnost i priguše oscilacije tijekom izvršavanja zadatka putem upravljanja pozicijom i silom. U ovom radu predložene su tri tehnike za poboljšanje performansi upravljanja omjerom rezonancija. Prvo, pokazano je kako novi observer poremećaja temeljen na više enkodera (MEDOB) estimira poremećajnu silu na strani tereta. Predloženi observer nije nužan za identifikaciju nominalnog koeficijenta opruge. Drugo, metoda koeficijentnog dijagrama (CDM) je primijenjena za proračun novog pojačanja regulatora sile. Iznos 2.0 je odre.en kao novo pojačanje omjera rezonancija. Konačno, MEDOB i observer poremećaja na strani tereta (LDOB) korišteni su za identifikaciju koeficijenta opruge sustava fleksibilnog robota. Predložena metoda identifikacije jednostavna je za implementaciju na stvarni sustav, te se pomoću nje jednostavno identificira koeficijent opruge. Učinkovitost predložene metode identifikacije provjerena je simulacijski i eksperimentalno

Comfort-Centered Design of a Lightweight and Backdrivable Knee Exoskeleton

This paper presents design principles for comfort-centered wearable robots and their application in a lightweight and backdrivable knee exoskeleton. The mitigation of discomfort is treated as mechanical design and control issues and three solutions are proposed in this paper: 1) a new wearable structure optimizes the strap attachment configuration and suit layout to ameliorate excessive shear forces of conventional wearable structure design; 2) rolling knee joint and double-hinge mechanisms reduce the misalignment in the sagittal and frontal plane, without increasing the mechanical complexity and inertia, respectively; 3) a low impedance mechanical transmission reduces the reflected inertia and damping of the actuator to human, thus the exoskeleton is highly-backdrivable. Kinematic simulations demonstrate that misalignment between the robot joint and knee joint can be reduced by 74% at maximum knee flexion. In experiments, the exoskeleton in the unpowered mode exhibits 1.03 Nm root mean square (RMS) low resistive torque. The torque control experiments demonstrate 0.31 Nm RMS torque tracking error in three human subjects.Comment: 8 pages, 16figures, Journa

Conceptual Study of Rotary-Wing Microrobotics

This thesis presents a novel rotary-wing micro-electro-mechanical systems (MEMS) robot design. Two MEMS wing designs were designed, fabricated and tested including one that possesses features conducive to insect level aerodynamics. Two methods for fabricating an angled wing were also attempted with photoresist and CrystalBond™ to create an angle of attack. One particular design consisted of the wing designs mounted on a gear which are driven by MEMS actuators. MEMS comb drive actuators were analyzed, simulated and tested as a feasible drive system. The comb drive resonators were also designed orthogonally which successfully rotated a gear without wings. With wings attached to the gear, orthogonal MEMS thermal actuators demonstrated wing rotation with limited success. Multi-disciplinary theoretical expressions were formulated to account for necessary mechanical force, allowable mass for lift, and electrical power requirements. The robot design did not achieve flight, but the small pieces presented in this research with minor modifications are promising for a potential complete robot design under 1 cm2 wingspan. The complete robot design would work best in a symmetrical quad-rotor configuration for simpler maneuverability and control. The military’s method to gather surveillance, reconnaissance and intelligence could be transformed given a MEMS rotary-wing robot’s diminutive size and multi-role capabilities

Finite element method for dynamic modelling of an underwater flexible single-link manipulator

In order to control the angular displacement of the hub and to suppress the vibration at the end point of an underwater flexible single-link manipulator system efficiently, it is required to obtain an adequate model of the structure. In this study, a mathematical model of an underwater flexible single-link manipulator system has been developed and modelled as a pinned-free, an Euler-Bernoulli flexible beam using finite element method based on Lagrangian approach analysis. Damping, hub inertia and payload are incorporated in the dynamic model, which is then represented in a state-space form. The simulation algorithm was developed using matlab and its performance, on the basis of accuracy in characterizing the behavior of the manipulator, is assessed