Simultaneous velocity, impact and force control

[EN] In this paper, we propose a control method to achieve three objectives simultaneously: velocity regulation during free motion, impact damping and finally force reference tracking. During impact, the parameters are switched in order to dissipate the energy of the system as fast as possible and the optimal switching criteria are deduced. The possibility of sliding regimes is analysed and the theoretical results are verified in simulations.We would like to thank the R&D&I Linguistic Assistance Office, Universidad Politecnica de Valencia (Spain), for Granting financial support for the linguistic revision of this paper. This work has been partially funded by the European project MASMICRO (Project number 500095-2), by the projects FEDER-CICYT with reference, DPI2005-08732C02-02 and DP12006-15320-C03-01, of the Ministry of Education and Science as well as by the research Project of the Generalitat Valenciana, GVPRE/2008 20080916.Zotovic Stanisic, R.; Valera Fernández, Á. (2009). Simultaneous velocity, impact and force control. Robotica. 27(7):1039-1048. https://doi.org/10.1017/S0263574709005451S1039104827710. Xu Y. , Hollerbach J. M. and Ma D. , “Force and Contact Transient Control Using Nonlinear PD Control,” Proceedings of the 1994 International Conference on Robotics and Automation (1994) pp. 924–930.Brach, R. M., & Goldsmith, W. (1991). Mechanical Impact Dynamics: Rigid Body Collisions. Journal of Engineering for Industry, 113(2), 248-249. doi:10.1115/1.2899694Chiaverini, S., & Sciavicco, L. (1993). The parallel approach to force/position control of robotic manipulators. IEEE Transactions on Robotics and Automation, 9(4), 361-373. doi:10.1109/70.246048Armstrong, B. S. R., Gutierrez, J. A., Wade, B. A., & Joseph, R. (2006). Stability of Phase-Based Gain Modulation with Designer-Chosen Switch Functions. The International Journal of Robotics Research, 25(8), 781-796. doi:10.1177/0278364906067543Volpe, R., & Khosla, P. (1993). A Theoretical and Experimental Investigation of Impact Control for Manipulators. The International Journal of Robotics Research, 12(4), 351-365. doi:10.1177/027836499301200403Impact modeling and control for industrial manipulators. (1998). IEEE Control Systems, 18(4), 65-71. doi:10.1109/37.710879Brogliato, B., Niculescu, S.-I., & Orhant, P. (1997). On the control of finite-dimensional mechanical systems with unilateral constraints. IEEE Transactions on Automatic Control, 42(2), 200-215. doi:10.1109/9.554400Brogliato, B. (1999). Nonsmooth Mechanics. Communications and Control Engineering. doi:10.1007/978-1-4471-0557-2Armstrong, B., & Wade, B. A. (2000). Nonlinear PID Control with Partial State Knowledge: Damping without Derivatives. The International Journal of Robotics Research, 19(8), 715-731. doi:10.1177/02783640022067120Controlling contact transition. (1994). IEEE Control Systems, 14(1), 25-30. doi:10.1109/37.257891Seraji, H. (1998). Nonlinear and Adaptive Control of Force and Compliance in Manipulators. The International Journal of Robotics Research, 17(5), 467-484. doi:10.1177/027836499801700501Volpe, R., & Khosla, P. (1993). A theoretical and experimental investigation of explicit force control strategies for manipulators. IEEE Transactions on Automatic Control, 38(11), 1634-1650. doi:10.1109/9.262033A nonlinear PD controller for force and contact transient control. (1995). IEEE Control Systems, 15(1), 15-21. doi:10.1109/37.341859Seraji, H., & Colbaugh, R. (1997). Force Tracking in Impedance Control. The International Journal of Robotics Research, 16(1), 97-117. doi:10.1177/027836499701600107Armstrong, B., Neevel, D., & Kusik, T. (2001). New results in NPID control: Tracking, integral control, friction compensation and experimental results. IEEE Transactions on Control Systems Technology, 9(2), 399-406. doi:10.1109/87.91139

Impact of inertia, friction, and backlash upon force control in telemanipulation

The mechanical behavior of master controllers of telemanipulators has been a concern of both designers and implementors of telerobotic systems. In general, the literature recommends that telemanipulator systems be constructed that minimize inertia, friction, and backlash in an effort to improve telemanipulative performance. For the most part, these recommendations are founded upon theoretical analysis or simply intuition. Although these recommendations are not challenged on their merit, the material results are measured of building and fielding telemanipulators that possess less than ideal mechanical behaviors. Experiments are described in which forces in a mechanical system with human input are evaluated as a function of mechanical characteristics such as inertia, friction, and backlash. Results indicate that the ability of the human to maintain gripping forces was relatively unaffected by dynamic characteristics in the range studied, suggesting that telemanipulator design in this range should be based on task level force control requirements rather than human factors

Learning Task Constraints from Demonstration for Hybrid Force/Position Control

We present a novel method for learning hybrid force/position control from demonstration. We learn a dynamic constraint frame aligned to the direction of desired force using Cartesian Dynamic Movement Primitives. In contrast to approaches that utilize a fixed constraint frame, our approach easily accommodates tasks with rapidly changing task constraints over time. We activate only one degree of freedom for force control at any given time, ensuring motion is always possible orthogonal to the direction of desired force. Since we utilize demonstrated forces to learn the constraint frame, we are able to compensate for forces not detected by methods that learn only from the demonstrated kinematic motion, such as frictional forces between the end-effector and the contact surface. We additionally propose novel extensions to the Dynamic Movement Primitive (DMP) framework that encourage robust transition from free-space motion to in-contact motion in spite of environment uncertainty. We incorporate force feedback and a dynamically shifting goal to reduce forces applied to the environment and retain stable contact while enabling force control. Our methods exhibit low impact forces on contact and low steady-state tracking error.Comment: Under revie

Experimental study of contact transition control incorporating joint acceleration feedback

Joint acceleration and velocity feedbacks are incorporated into a classical internal force control of a robot in contact with the environment. This is intended to achieve a robust contact transition and force tracking performance for varying unknown environments, without any need of adjusting the controller parameters, A unified control structure is proposed for free motion, contact transition, and constrained motion in view of the consumption of the initial kinetic energy generated by a nonzero impact velocity. The influence of the velocity and acceleration feedbacks, which are introduced especially for suppressing the transition oscillation, on the postcontact tracking performance is discussed. Extensive experiments are conducted on the third joint of a three-link direct-drive robot to verify the proposed scheme for environments of various stiffnesses, including elastic (sponge), less elastic (cardboard), and hard (steel plate) surfaces. Results are compared with those obtained by the transition control scheme without the acceleration feedback. The ability of the proposed control scheme in resisting the force disturbance during the postcontact period is also experimentally investigated

A mathematical model of an active control landing gear for load control during impact and roll-out

A mathematical model of an active control landing gear (ACOLAG) was developed and programmed for operation on a digital computer. The mathematical model includes theoretical subsonic aerodynamics; first-mode wing bending and torsional characteristics; oleo-pneumatic shock strut with fit and binding friction; closed-loop, series-hydraulic control; empirical tire force-deflection characteristics; antiskid braking; and sinusoidal or random runway roughness. The mathematical model was used to compute the loads and motions for a simulated vertical drop test and a simulated landing impact of a conventional (passive) main landing gear designed for a 2268-kg (5000-lbm) class airplane. Computations were also made for a simply modified version of the passive gear including a series-hydraulic active control system. Comparison of computed results for the passive gear with experimental data shows that the active control landing gear analysis is valid for predicting the loads and motions of an airplane during a symmetrical landing. Computed results for the series-hydraulic active control in conjunction with the simply modified passive gear show that 20- to 30-percent reductions in wing force, relative to those occurring with the modified passive gear, can be obtained during the impact phase of the landing. These reductions in wing force could result in substantial increases in fatigue life of the structure

Measurement of Impact Forces on Teeth and Jaw when Wearing Sports Mouth Guards

The objective of this project is to accurately measure the forces the teeth and jaw experience when subjected to impact. For this purpose piezoelectric technology (PVDF), which converts voltage to force and vice versa can be used to measure forces applied to teeth. A PVDF cable is calibrated and used for measuring force along with a control measuring device (PCB Piezotronics). The method involves wrapping the PVDF cable around a 3D home-printed, customized denture. The cable was chosen due to the fact that it allows for adequate fit between mouth guard and denture. Two masses, a baseball and 2 lbs - 3D printed projectile, were dropped from a height of 1m onto the denture with and without mouth guard. Results showed a significant force absorption by the mouth guard (more than 50% of initial impact force). After several trials, (n=10 for each group, baseball with and without mouthguard, as well as 2lbs), it was found that the impact shock absorption by the mouth guard ranged between 60-70%. Figure 1 shows the values at which the denture was impacted, with and without a mouth guard for baseball and 2 lbm cylinder. Finally, FEA Analysis was also used to show the regional stress and strain along the denture.https://scholarscompass.vcu.edu/capstone/1201/thumbnail.jp

RF-MEMS switch actuation pulse optimization using Taguchi's method

Copyright @ 2011 Springer-VerlagReliability and longevity comprise two of the most important concerns when designing micro-electro-mechanical-systems (MEMS) switches. Forcing the switch to perform close to its operating limits underlies a trade-off between response bandwidth and fatigue life due to the impact force of the cantilever touching its corresponding contact point. This paper presents for first time an actuation pulse optimization technique based on Taguchi’s optimization method to optimize the shape of the actuation pulse of an ohmic RF-MEMS switch in order to achieve better control and switching conditions. Simulation results show significant reduction in impact velocity (which results in less than 5 times impact force than nominal step pulse conditions) and settling time maintaining good switching speed for the pull down phase and almost elimination of the high bouncing phenomena during the release phase of the switch

Suppress vibration on robotic polishing with impedance matching

Installing force-controlled end-effectors on the end of industrial robots has become the mainstream method for robot force control. Additionally, during the polishing process, contact force stability has an important impact on polishing quality. However, due to the difference between the robot structure and the force-controlled end-effector, in the polishing operation, direct force control will have impact during the transition from noncontact to contact between the tool and the workpiece. Although impedance control can solve this problem, industrial robots still produce vibrations with high inertia and low stiffness. Therefore, this research proposes an impedance matching control strategy based on traditional direct force control and impedance control methods to improve this problem. This method's primary purpose is to avoid force vibration in the contact phase and maintain force-tracking performance during the dynamic tracking phase. Simulation and experimental results show that this method can smoothly track the contact force and reduce vibration compared with traditional force control and impedance control

Estimation of changes in the force of infection for intestinal and urogenital schistosomiasis in countries with Schistosomiasis Control Initiative-assisted programmes

The last decade has seen an expansion of national schistosomiasis control programmes in Africa based on large-scale preventative chemotherapy. In many areas this has resulted in considerable reductions in infection and morbidity levels in treated individuals. In this paper, we quantify changes in the force of infection (FOI), defined here as the per (human) host parasite establishment rate, to ascertain the impact on transmission of some of these programmes under the umbrella of the Schistosomiasis Control Initiative (SCI)