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In this paper, we propose three methods to compute low-latency analog position where two of them fuse encoder and rate gyro signals. While one method is based on gyro with bias correction using encoder information, the other one is encoder-referenced combined with a resettable integrator to minimize the staircase form of encoder signals. Experiments on a one degree-of-freedom haptic simulation system have shown that a low-latency analog position with an accuracy over 98% compared to the sampled encoder signal can be obtained. The analog position signals are then utilized to produce analog viscoelastic virtual environments to assess and benchmark the proposed methods through uncoupled stability and perceived fidelity tests. The results have shown that a virtual stiffness range larger than 400% can be obtained with enhanced fidelity compared to common digital implementations.

The stability of haptic simulation systems has been studied for a safer interaction with virtual environments. In this work, the passivity, uncoupled stability, and fidelity of such systems are analyzed when a viscoelastic virtual environment is implemented using a general discretization method that can also represent methods such as backward difference, Tustin, and zero-order-hold. Dimensionless parametrization and rational delay are considered for device independent analysis. Aiming at expanding the virtual environment dynamic range, equations to find optimum damping values for maximize stiffness are derived and it is shown that by tuning the parameters for a customized discretization method, the virtual environment dynamic range will supersede the ranges offered by methods such as backward difference, Tustin and zero-order-hold. It is also shown that minimum time delay is required for stable Tustin implementation and that specific delay ranges must be avoided. The proposed discretization method is numerically and experimentally evaluated.

Absolute stability analysis of bilateral teleoperation systems are typically model-based. Under borderline conditions of absolute stability, depending on the degree of uncertainty in the dynamic model of the teleoperator and existing noise, the system may behave as potentially unstable when the model-based analysis predicts otherwise. In this article, we propose a methodology to experimentally verify the absolute stability of master-slave teleoperation systems. Since absolute stability demands bounds of all possible environments, we achieve this by conducting only three experiments that are often experienced in teleoperation: free slave, mass-carrying slave and locked slave (rigid environment). We will validate and compare our proposed method with the benchmark Llewellyns absolute stability criterion. Furthermore, we will examine the robustness of the proposed method and will provide guidelines for choosing the mass for the mass-carrying load condition.

Haptic simulation systems, which typically implement virtual environments in the discrete-time domain, present an inherent trade-off between stability, sampling frequency, and the range of implementable environment dynamics. Previous research has demonstrated the potential of analog feedback for expanding the range of environment dynamics that result in a stable haptic interaction. In this paper, the effect of various system parameters on the environment dynamic range is analytically and experimentally investigated in the sense of uncoupled stability. In addition, Multilayer Decomposition, which enables a simple analog PD controller to implement nonhomogeneous or multilayer virtual environment dynamics, will be presented and evaluated.

We present the research advances on the development of 50-200 mJ energy range diode-pumped Yb:CaF2- based multipass amplifiers operating at relatively high repetition rates. These laser amplifiers are based on diverse innovative geometries. All these innovations aim to design compact, stable and reliable amplifiers adapted to our application that consists in pumping ultrashort-pulse OPCPA (optical parametric chirped pulse amplifier) systems in the frame of the Apollon 10 PW laser project. The targeted repetition rate is in the range of 20-100 Hz with energies of few tens of mJ for the first stages up to 1 J for the final stage. An analysis of the specificities of Yb:CaF2 is done to explain the different options we chose to fulfil these specifications. The critical points and limitations of the multipass Yb:CaF2-based amplifiers are subsequently discussed. To overcome the encountered problems, different issues are investigated such as crystal optimisation, laser head geometry, thermo-optical dynamics or coherent combining techniques. Experimental results for different multipass configurations are demonstrated and discussed.

In this paper, we propose an approach to the control of linear teleoperation systems under time delays. Unlike traditional delay-robust control systems that guarantee passive communication channel through the transmission of wave variables, the new approach uses the concept of absolute stability for the physically expressive Lawrence's four-channel structure for transmitting the standard power variables, i.e., force and position. By incorporating kinesthetic performance requirements, we derive an absolutely stable four-channel controller that is transparent when time delay is negligible. Experimentally, the study evaluates and compares the performance of the proposed controller with that of a benchmark wave variable-based controller. The results indicate contact stability for large delays, a lack of position drift, and improved position and force tracking in both the free motion and rigid contact regimes for small delays.