This paper presents a novel flexible chest harness for upper-body exoskeletons and evaluates its effect on upper-body kinematics using a model-based motion capture system. The harness combines a frontal and dorsal plate with flexible ``tentacles'' that conform to the torso, distributing load while preserving free breathing and shoulder motion. Five healthy participants performed thirteen prescribed upper-body movements with and without the harness while joint angles were recorded using the HumanTrak 3D motion analysis system. The model-based kinematic data show minimal changes in neck range of motion ($-2.6\%$ to $+0.1\%$) and small reductions in shoulder and trunk mobility, with the largest decreases in shoulder internal rotation ($-5.4\%$) and trunk rotation ($-4.7\%$). Participants reported improved comfort and stability compared with conventional rigid strap arrangements. The results indicate that the proposed harness can provide secure upper-body fixation for exoskeletons while largely preserving natural motion, supporting its use as a human--robot interface component in future industrial and rehabilitation systems.

Lower-limb rehabilitation exoskeletons often require time consuming setup and provide assistance that is only loosely coupled to user intention. This paper presents a lightweight proof-of-concept knee exoskeleton that combines surface electromyography (sEMG) intention sensing with dual inertial measurement units (IMUs) for closed-loop angle correction. A calibrated mapping model converts sEMG activity to a target knee angle, while a discrete time controller drives antagonistic string actuation to reduce the tracking error. To improve usability, an automated calibration sequence with audio guidance is delivered over an IoT link to a companion computer, which also logs synchronised run-time data. In benchtop trials, the prototype supports approximately 0◦–120◦knee motion, weighs about 1 kg, and achieves target–measured agreement within 10◦with an observed response delay below 1.5 s. Calibration completes in under 90 s. The main contribution is an integrated sensing–control–interaction pipeline that is simple to replicate and provides a clean basis for modelling and simulation studies of assistive control behaviour.

Expressive humanoid heads are increasingly used in social robotics, education, and interactive simulation environments, yet their mechanical complexity and tight packaging constraints often lead to long build--test cycles. This paper presents a simulation-driven workflow for designing and validating a proof-of-concept biomimetic robotic head capable of producing recognisable facial expressions. A modular kinematic architecture (neck, jaw, eye, and eyebrow subsystems) is modelled in CAD, where joint constraints and motion envelopes are simulated to verify feasibility before fabrication. The resulting prototype integrates 26 servo actuators within a human-head form factor (mass 1.5 kg) and employs a discrete-time smoothing strategy to shape actuator commands and reduce mechanical transients, improving the perceived naturalness of motion. The contribution of this work is twofold: (i) a repeatable model-based design procedure that links simulation artefacts to physical integration, and (ii) an initial set of implementation insights that reduce risk in future upgrades toward perception-driven expression control and a digital twin for human--robot interaction studies.

Passivity has been the most often used constraint for the stable controller design of bilateral teleoperation systems. Especially, Time Domain Passivity Approach (TDPA) has been used in many applications since it has been known as one of the least conservative passivity-based approaches. Although TDPA were able to stabilize the system with the least conservatism, it has its own drawbacks as the cost of achieving the least conservative passivity especially when there is communication time-delay. Due to the on/off bang-bang control-like modification for instantaneous passivity recovery, it has high frequency force vibrations on the slave and especially master side. By implementing a virtual mass-spring system between the passivity controller and master device, these high frequency vibration has been eliminated. However, the gains need proper tuning as they are dependent on the teleoperation setup and application. It also tends to make the system sluggish which further distorts the transparency. We propose a new observer-based gradient controller to eliminate the force jittering on the master side. It rectifies the delayed feedback force by removing the undesired increase in force which is generated by the delay in communication channel. It does not require any system parameters and there are no gains to tune, thus it can be added to any teleoperator irrespective of its dynamics and without having any prior system information. The proposed approach was implemented to a position-force bilateral teleoperation system, and compared with TDPA with virtual mass spring with round-trip delays of up to 500 ms for hard wall contacts.

The process of designing bio-inspired knee joint for prosthetics/exoskeletons has been a challenging issue due to the complicated relationships between the performance criteria and the link lengths of the design space, or workspace in the case of manipulators. This paper address this issue by presenting numerical analysis and design methodology that have been used for mapping the design space of a bio-inspired knee joint. Four aspects of performance are modelled: peak mechanical advantage, RMS (root mean square) mechanical advantage, RMS sliding ratio, and range of movement. The performance of the joint is dependent on the shape of the condylar surfaces and the geometry of the four-bar mechanism. The results of the complete map for the design space are characterized by the mechanical advantage, sliding ratio and the range of movement that mimics the human knee joint with the movement of rolling and sliding between the condylar surfaces of the femur and tibia. Therefore, several design charts are proposed accordingly to facilitate the selection of designers of the optimal configuration adapted to their specific application. Based on our numerical analysis performed on the proposed bio-inspired knee joint model, the performance maps demonstrated that there is an estimated reduction of 30% for the actuator required force.

Enhancing transparency of a teleoperation system by increasing the command-following bandwidth has not received lots of attention so far. This is considered a challenging task since in a teleoperation system the command-following bandwidth of the slave robot motion controller cannot be increased with a conventional motion controller as the desired trajectory is instantaneously commanded by the human user and thus, cannot be considered to be given in a pre-computed, smooth second order derivative form. We propose a method to increase the command-following bandwidth by extending the previously introduced Successive Stiffness Increment (SSI) approach to bilateral teleoperation. The approach allows realizing a very high motion controller gain, which cannot be realized with a conventional bilateral teleoperation controller as confirmed by experimental results.

This paper proposes an approach to enlarge the impedance range of admittance-type haptic interfaces. Admittance-type haptic interfaces have advantages over impedance-type haptic interfaces in the interaction with high impedance virtual environments. However, the performance of admittance-type haptic interfaces is often limited by the lower boundary of the impedance that can be achieved without stability issue. Especially, it is well known that low value of inertia in an admittance model often causes unstable interaction. This paper extends recently proposed input-to-state stable approach [1] to further lower down the achievable impedance in admittance-type haptic interfaces with less conservative constraint compared with the passivity-based approaches. The primary challenge was identifying the nonlinear hysteresis components which are essential for the implementation of the input-to-state stable approach. Through experimental investigation and after separating and merging the admittance model and the position controller, the partial admittance model (from the measured human force to the desired velocity) and the velocity controller (from the velocity tracking error to the controller force) were found having counter-clockwise hysteresis nonlinear behavior. Therefore, it allows implementing the one-port input-to-state stable (ISS) approach for making both components dissipative and ISS. An additional advantage of the proposed ISS approach is the easiness of the implementation. No model information is required, and the network representation is not necessary, unlike the passivity-based approaches. Series of experiments verified the effectiveness of the proposed approach in term of significantly lowering the achievable impedance value compared with what the time-domain passivity approach can render.

Passivity has been a major criterion for designing a stable haptic interface due to its numerous advantages. However, passivity-based controllers have suffered from the design conservatism of the passivity criterion, particularly when users want to increase the maximum apparent impedance. Based on the input-to-state stable (ISS) criterion and an analogy between haptic interfaces and systems with hysteresis, this paper proposes a control framework that is less conservative than passivity-based controllers. The proposed ISS approach allows a non-predetermined finite amount of output energy to be extracted from the system. Therefore, the proposed method can increase the maximum apparent impedance compared with passivity-based approaches. The focus of this paper is on how the proposed approach is designed to satisfy the input-to-state stability criterion in real time without prior knowledge of the system. This paper also extends the primary single-port ISS approach to a two-port ISS approach for multiple-degree-of-freedom generalization. The experimental and numerical results demonstrate that the proposed ISS approach is able to stabilize a higher impedance range than the time-domain passivity approach. The experimental results also confirm that the proposed approach provides higher actual apparent impedance to the operator compared with the energy-bounding and force-bounding approaches.

Passivity has been the most often used constraint for the controller design of haptic interfaces. However, the designed controller based on passivity constraint has been suffering from its conservatism, especially when the user wants to increase the maximum achievable impedance. To overcome this problem, our group have proposed Input-to-State Stable (ISS) approach [1], which reduce the design conservatism of the passivity-based controller by allowing bigger output energy from the haptic interface compared with the passivity-based controller while guaranteeing the stability. However, the previous paper was limited to single Degree-of-Freedom (DoF) systems. This paper extends the ISS approach for multi-DoF haptic interaction. For multi-DoF haptic interaction, penetration depth-based rendering method using Virtual Proxy (VP) is adopted, and VP allows us to decouple the interaction into each axis. Although the interaction can be decoupled, previous ISS analysis “cannot” be directly implemented because the decoupled system, unlike to the previous case, has unconstrained end point, that is a moving Virtual Environment (VE). To include the moving VE into the ISS approach, we extend the previous one-port ISS approach to two-port ISS approach, and generalize this into multi-DoF ISS approach by augmenting each two-port analysis. Proposed approach is experimentally verified with Phantom Pre. 1.5, and showed the effectiveness of the proposed multi-DoF ISS approach.

Passivity has been a major criterion on designing a stable haptic interface due to many advantages. However, passivity has been suffering from its intrinsic conservatism since it only represents a small set of the whole stable region. Therefore, there was always limitation to increase the performance due to the small design margin from the passivity criterion. In most of the cases, stability and performance has trade-off relationship. In this paper, we propose a less conservative control approach for stable haptic interaction based on Input to State Stable (ISS) criterion. The proposed approach is inspired from the analogy between virtual environments and systems with hysteresis nonlinearities. A system with hysteresis nonlinearity has sector bounded property, which allows us to guarantee that only a finite amount of energy can be extracted from the system, which leads the system to be dissipative [1] and also the states to be bounded by a function of the input [2]. Since the finite amount of energy is allowed to be extracted from the system, the proposed ISS approach has less conservative constraint compared with passivity-based approaches. Moreover, the proposed approach has a simple structure and does not use any system parameters which make it suitable for practical implementations. Experimental evaluation validates the effectiveness of the proposed approach.

Passivity has been the most often used constraint for the controller design of bilateral teleoperation systems. However passivity has been suffering from its own design conservatism since this is a sufficient condition for stability and representing only a small set of overall stability region. In our previous works [1], [2], a less conservatism control approach, we named it Input-to-Sate Stable (ISS) approach, has been introduced for reducing the intrinsic design conservatism of the passivity-based controllers by allowing bigger output energy compared with the passivity-based controller while guaranteeing the stability. However the previous works were limited to haptic interfaces, which is interacting with computer generated virtual environments. In this paper, we extended the ISS approach for bilateral teleoperation systems. For this extension, the previous one-port ISS approach was generalized to two-port ISS approach. The main difficulty of this extension was identifying the signal pair to show hysteresis nonlinear behavior. By introducing a linear function assumption for two-port bilateral controller, which is generally acceptable, we could formulate two-port ISS approach. The extended two-port approach was implemented to a position-force bilateral teleoperation system, and the performance was experimentally verified with a dual Phantom teleoperation system.

This paper proposes a method to increase the impedance range of admittance-type haptic interfaces. Admittance-type haptic interfaces are used in various applications that typically require interaction with high impedance virtual environments. However, the performance of admittance haptic interfaces is often judged by the lower boundary of the impedance that can be achieved without stability problem; in particular, minimum displayable inertia. It is well known that rendering the low value of inertia makes the admittance-type haptic interfaces unstable easily. This paper extends Time Domain Passivity Approach (TDPA) to lower down the minimum achievable inertia in an Admittance-type haptic interface. To use the well-developed TDPA framework, an admittance haptic interface should be represented in network domain with clear energy flows, which was not straightforward due to unclear causality. Therefore by introducing dependent effort and flow source concept, the admittance type haptic interface is represented in electrical network domain. This network representation allows us to have clear causality, and consequently allowing to implement TDPA. The proposed idea was experimentally verified, and found successful in bringing down the minimum inertia 10 times lower than without TDPA case.