Contact modeling as applied to the dynamic simulation of legged robots

The recent studies in robotics tend to develop legged robots to perform highly dynamic movement on rough terrain. Before implementing on robots, the reference generation and control algorithms are preferably tested in simulation and animation environments. For simulation frameworks dedicated to the test of legged locomotion, the contact modeling is of pronounced signi cance. Simulation requires a correct contact model for obtaining realistic results. Penalty based contact modeling is a popular approach that de nes contact as a spring - damper combination. This approach is simple to implement. However, penetration is observed in this model. Interpenetration of simulated objects results in less than ideal realism. In contrast to penalty based method, exact contact model de nes the constraints of contact forces and solves them by using analytical methods. In this thesis, a quadruped robot is simulated with exact contact model. The motion of system is solved by the articulated body method (ABM). This algorithm has O(n) computational complexity. The ABM is employed to avoid calculation of the inverse of matrices. The contact is handled as a linear complementarity problem and solved by using the projected Gauss Seidel algorithm. Joint and contact friction terms consisting of viscous and Coulomb friction components are implemented

Simplified dynamic model for the control of a surgical robot

Bu çalışmanın temel konusu minimal invaziv tipi bir ameliyat olan endoskopik hipofiz tümörü ameliyatında kullanılan endoskopun hareket denetimi için geliştirilen robotik sistemdir. Geliştirilen sistemin bu bildiride ele alınan kısmı, ameliyat sırasında sadece ameliyat bölgesi içinde endoskopu cerrahın anlık isteklerine göre yönlendiren, aktif robot yapısıdır. Söz konusu robot uzak hareket merkezli, 3 serbestlik dereceli, paralel kinematik mimariye sahiptir. Bu çalışmada robotun denetimi için uygun görülen hesaplanmış tork yöntemi için gerekli robotun dinamik analizi sunulmaktadır. Denetim algoritmasının yüksek frekansta çalışabilmesi için dinamik denklemlerde yapılan basitleştirmeler ve bunun sonucunda elde edilen hesaplama zamanı sunulmaktadır.The fundamental subject of this study is the robotic system developed for the motion control of the endoscope used in the pituitary tumor surgery, which is a type of minimally invasive surgery. The part of this developed system issued in this paper is the active robot that directs the endoscope according to the instantaneous demands of the surgeon only in the surgical area. The robot has a remote-center-of-motion, 3 degrees-offreedom and parallel kinematic architecture. In this paper, dynamic analysis of the robot is presented. The dynamic analysis is required for the computed torque method. The paper is concluded by reporting the simplifications that are done in the dynamic equations in order to enable higher frequency of operation of the control algorithm and the resulting computation time.TÜBİTAK Proje Numarası: 115E72

The effects of admittance term on back-drivability

4th Conference on Mechanisms, Transmissions and Applications, MeTrApp 2017; Trabzon; Turkey; 3 July 2017 through 5 July 2011In the design of kinesthetic haptic devices, there are mainly impedance type and admittance type device. In a customary scenario, the human operator back-drives the haptic device by holding and providing motion to the handle of the haptic device. If the type of transmission system does not allow passive back-drivability, then the back-drivability is satisfied by the use of an admittance controller. This type of a haptic device is said to have admittance structure. The selection of the admittance term in this controller plays a critical part in the task execution performance. Determination of this term is not trivial and the optimal parameters depend on not only the key performance criteria but also on the human operator. An experimental study is carried out in this work to determine the effect of the admittance term parameters on the performance of human operators in terms of the energy efficiency and the best accuracy. In this paper, the experimental set-up and the results of the experiments are presented and discussed.The Scientific and Technological Research Council of Turkey (115E726

A novel method for slip prediction of walking biped robots

This paper proposes a new approach for slip prediction of walking biped robots. The slip prediction is a measurement-based and friction behavior-inspired approach. A measurement-based online algorithm is designed to estimate the Coulomb friction which is regarded as a slip threshold. To predict the slip, a safety margin is introduced in the negative vicinity of the estimated Coulomb friction. The estimation algorithm concludes that if the applied force is outside the safety margin, then the foot tends to slip. The proposed approach depends on the available type of measurements. Three options of measurements are discussed. Among them, the foot acceleration and ankle force measurements scenario is validated by experiments on the humanoid SURALP (Sabanci University Robotics Research Laboratory Platform). The results demonstrate the effectiveness of the proposed approach for slip prediction and detection

Toward safe and high-performance human-robot collaboration via implementation of redundancy and understanding the effects of admittance term parameters

Today, demandsin industrial manufacturing mandate humans to work with large-scale industrial robots, and this collaboration may result in dangerous conditions for humans. To deal with this situation, this work proposes a novel approach for redundant large-scale industrial robots. In the proposed approach, an admittance controller is designed to regulate the interaction between the end effector of the robot and the human. Additionally, an obstacle avoidance algorithm is implemented in the null space of the robot to prevent any possible unexpected collision between the human and the links of the robot. After safety performance of this approach is verified via simulations and experimental studies, the effect of the parameters of the admittance controller on the performance of collaboration in terms of both accuracy and total human effort is investigated. This investigation is carried out via 8 experiments by the participation of 10 test subjects in which the effect of different admittance controller parameters such as mass and damper are compared. As a result of this investigation, tuning insights for such parameters are revealed

A novel method for slip prediction of walking biped robots

This paper proposes a new approach for slip prediction of walking biped robots. The slip prediction is a measurement-based and friction behavior-inspired approach. A measurement-based online algorithm is designed to estimate the Coulomb friction which is regarded as a slip threshold. To predict the slip, a safety margin is introduced in the negative vicinity of the estimated Coulomb friction. The estimation algorithm concludes that if the applied force is outside the safety margin, then the foot tends to slip. The proposed approach depends on the available type of measurements. Three options of measurements are discussed. Among them, the foot acceleration and ankle force measurements scenario is validated by experiments on the humanoid SURALP (Sabanci University Robotics Research Laboratory Platform). The results demonstrate the effectiveness of the proposed approach for slip prediction and detection