The state-of-the-art teleimpedance command interfaces used to command the robot stiffness configuration are either too complex to set up, such as those that use physiological signals and other tracking methods or cannot configure the stiffness appropriately for 3d environments. To mitigate these issues, a novel teleimpedance interface is proposed. The proposed interface can independently control the stiffness configuration’s shape, orientation, and size with single-hand operations while allowing the operator to use that hand to command the robot’s position. The teleimpedance interface is attached to the operator’s hand and uses two scroll wheels, a joystick, and a force sensor to configure the robot’s stiffness and has two different modes of operation. Compared to the state-of-the-art methods, the main advantage of the proposed teleimpedance command interface is that it does not require additional hardware with force feedback or complex setup calibrations while allowing for control of the robot’s 3D stiffness configuration with single-handed operation. An experiment with human subjects was performed to demonstrate the proposed interface’s acceptance and functionality. To demonstrate the teleimpedance command interface’s ability to adjust 3D stiffness configurations a teleoperation was performed, utilizing a Kuka robotic arm and a Force Dimension Sigma7 position input interface. The teleimpedance interface functioned as intended during teleoperation in a 3D environment to configure and adjust the 3D stiffness configuration for the task in real-time. The results from the human subject trials indicate that the participants can successfully operate the interface to complete the alignment tasks in both modes for 3D stiffness configurations.

This research investigates methodologies to reduce and implement negative inertia in robots for upper extremity diagnostics and rehabilitation. The robot’s responsiveness is enhanced by integrating accelerometers and Kalman filters into the control scheme, ensuring smoother physical human-robot interactions. A force gain that mimics negative inertia significantly improves system dynamics within the admittance control framework. Introducing dead zones for force and acceleration stabilizes responses at lower rendered inertia, crucial for handling spastic conditions. However, this research identifies a lack of standardized evaluation methods for negative inertia and highlights hardware constraints, such as bandwidth limitations, that restrict performance. Future research should focus on establishing evaluation standards and optimizing hardware to refine control precision. This work demonstrates the potential of advanced control strategies to optimize robotic rehabilitation, paving the way for more effective diagnostic and therapeutic interventions.

Stroke causes severe tactile deficiencies, affecting motor control during object grasping and lifting. Understanding the fundamental neural disorders associated with tactile deficits is crucial for developing effective rehabilitation and treatment plans. Previous studies have investigated the dynamics between finger grasping behavior and arm muscle activation in stroke patients. However, the exact neuromuscular synergy between tactile perception and arm usage remains unexplored. In this study, we designed a comprehensive experimental platform and tested potential synergies in 12 healthy young adults, serving as a control group to establish a foundation for future studies on stroke patients. The experimental platform consists of a lever arm on which torques can be applied to the subject's arm. The end effector is equipped with a special ultrasonic friction modulation plate that can reduce apparent friction by up to 63%, simulating real-world grasping tasks in a controlled setting. The experiments were conducted under varying conditions of friction and arm usage. Results indicate significant effects of tactile stimulation on grasping force adaptation (p < 0.05 in 8 of 12 experimental conditions). In contrast, arm usage did not show significant synergy with tactile perception (p = 0.44 for grasping force adaptation amplitude, and p = 0.73 for reflex delay). These findings demonstrate that the experimental platform can provide insights into human tactile behaviors, which is critical for studying the synergy between tactile sensory and motor control. The results will lay the groundwork for future research on underlying pathologies and rehabilitation strategies for stroke patients.

Soft robots offer a variety of useful applications. However, the nature of their design makes them challenging to control using traditional techniques. Many applications therefore rely on machine learning-based methods, learning opaque control policies or dynamic models of the robot. This often results in overly complex and uninterpretable solutions for the problem at hand.
In this paper, a simplified approach is considered: Using a common feedforward neural network as a target adapter module, learned adaptations are added to the desired targets that are fed to a simple PID controller, essentially “deceiving” it into a better performance. This adapter is completely separate from the controller itself, allowing for relatively simple controllers to control and adapt to complex and evolving systems.
The approach is tested in simulation on a simple mass-springdamper control problem, where qualitative results show nearimmediate improvement in controller performance. The approach is then tested on a demonstrator origami robot, which relies for its functionality on the dynamics of the Kresling origami spring. Results show that this simple adaptation approach is robust to changes in controller tuning and changes in system dynamics. However, the method is sensitive to the sampling frequency at which training data is recorded.

Metamaterials are tessellated structures that introduce unique properties to motion system applications. The research on behaviour changes caused by this tessellation remains limited. This paper outlines the change in behaviour from a compliant unit cell to a metamaterial motion system, regarding linear stiffness, range of motion (RoM) and crosstalk. These properties are achieved through the analysis of series and parallel configurations, as well as scaling variations. The concept of an ideal shear cell is presented, describing desired motion system characteristics. Roberts mechanism approximates the ideal shear cell, bringing embodiment for finite element analysis and experimental validation. Results indicate that parallel configurations increase stiffness, while series arrangements reduce it, with RoM and crosstalk displaying opposing trends. Additionally, variations in flexure thickness introduce a trade-off between stiffness and range of motion. Different scaling strategies affect overall stiffness with minimal impact on RoM and crosstalk. While the main findings do not indicate inherent performance benefits to compliant mechanisms. This research contributes valuable insights into the design and performance of metamaterial-based motion systems, providing a foundational framework for future studies and applications.

Robot dexterous manipulation research has drawn more attention in recent years since the development of various learning methods makes it possible for robots to achieve dexterity at the human level. Many attempts have been made to integrate human knowledge into Reinforcement Learning (RL) processes for faster learning speed and better performance. Despite their successes in many aspects, there are two open problems that still need to be carefully considered: 1. The effect of demonstrations gradually vanishes during RL. 2. In most cases, only imperfect demonstrations are available to robots. In this work, we proposed a new learning framework - Interactive Behavioural Cloning for faster Reinforcement Learning (IBC-RL), which could alleviate problems in complex manipulation tasks with long horizons. Different demonstrations are shown to robots at different learning stages. Robots learn complex tasks step by step with interactive demonstrations from human teachers. The framework is evaluated with four dexterous manipulation tasks simulated with the Isaac Gym engine. Human teachers perform demonstrations by controlling the simulated robot hands through a hand-tracking system. The results of the experiments could demonstrate the efficiency of IBC-RL in guiding and accelerating the learning processes with imperfect demonstrations.

Navigating touchscreens in vehicles becomes increasingly challenging when subjected to external perturbations like air turbulence or bumpy roads. These perturbations can lead to a loss in task performance, reduced finger accuracy, and increased frustration among users. To address these issues, electrovibration has emerged as a promising technology to enhance touchscreen interactions by providing users with better feedback and maintaining touch stability even under challenging conditions. Before we investigate if electrovibration helps users in challenging conditions, first the effects of external perturbations on tactile perception by electrovibration must be found. To investigate the impact of external perturbations on electrovibration perception, we conducted psychophysical experiments with 18 participants interacting with an electrostatic display mounted on the cockpit of the SIMONA flight simulator. We measured participants’ absolute detection thresholds for electrovibration pulses generated using 100 Hz input voltage for durations of 0.2 and 0.5 seconds, simulating a ridge and a button or slider. The measurements were taken under no-turbulence conditions and two different turbulence conditions. Our results revealed that turbulence significantly affects vertical finger movement, average normal force, and the change in force applied to the screen by participants. This combination of factors, along with the 0.2-second pulse duration, makes electrovibration more difficult to perceive or even imperceptible. The 0.5-second electrovibration pulse was perceived better overall and remained unaffected by turbulence. This highlights the strong significance of pulse duration on the absolute threshold of electrovibration. Therefore, to counteract the negative effects of perturbations on perception, electrovibration should be employed for longer durations when perturbations are present.

The provision of somatosensory information may play a fundamental role in the recovery of stroke patients. Particularly, tactile information is known to influence motor control by contributing to the perception of the weight, friction, and slip condition of objects. Despite this, the inclusion of tactile information through haptic rendering in robotic neurorehabilitation systems remains largely unexplored. In this study, we present a tactile interface to extend the kinesthetic rendering capabilities of an existing hand rehabilitation robot. The developed solution relies on skin stretch stimulation of the fingerpads, which allows the rendering of interaction forces with tangible virtual objects, e.g., friction, weight, and inertia. In contrast with previous skin stretch devices, our system uses closed-loop force control for accurate force rendering, relying on a custom magnetic field-based three-axis force sensor. A three-axis positioning stage in combination with a reference force sensor was used for calibrating and characterizing the sensor, as well as evaluating the interface response. The sensor achieves shear force accuracies of 0.2 N, influenced by hysteresis and viscoelastic creep effects. The tactile interface achieves a steady-state error of 0.2–0.4N and rise times of 20–70 ms during step response tests. Frequency response tests show that the interface can successfully track signals up to 5–7 Hz. The novel use of force-controlled skin stretch stimulation aims to open a new avenue for the accurate rendering of interaction forces through the tactile sense. Moreover, through purposeful design for usage in the rehabilitation domain, we hope that this study will serve as a stepping stone toward the inclusion of tactile information in robot-assisted therapies.

The emergence of tactile technologies has paved the way for addressing various challenges. Tactile sensing is especially vital for the blind and visually impaired. This study investigates how tactile feedback can enhance mobility and independence among individuals in this community. In today’s touchscreen-dominated world, accessibility remains a critical concern for those who are visually impaired, as touchscreens lack the tactile guidance necessary for effective touchscreen use. In addition, it is investigated if the guidance is useful for orientation. Our innovative approach employs a directional friction modulation rendering method, aiding users in finger movement and orientation. The efficacy of the tactile directional cue will be assessed for a tracking task and an orientation task. The tactile cue’s shape is determined by the parameter σ, which we optimize in our research. Additionally, in the orientation experiment, we explore the impact of different Field of Feeling ranges, representing the maximum perceivable angles on the actuated glass plate. Our methodology involves blindfolded participants in experiments assessing their ability to interpret and respond to tactile cues generated by an ultrasonic friction modulation device. We use quantitative measures, including response time and directional accuracy, and qualitative feedback from questionnaires to capture participants’ experiences with the tactile feedback system. Our findings reveal fascinating insights into the influence of σ and the Field of Feeling. On average the paths were tracked with an error of 9.84 mm. Smaller σ values correlate with improved tracking performance, as evidenced by the lower root-mean-square error between the finger and the reference path. This relationship is described using a logistic function. The directional friction modulation rendering method was shown to be viable for finding the reference angle. On average, this was achieved in 10.79 seconds with a manageable error of 6.28 ◦ . Specific differences between the tested values for σ were not found. In contrast, the Field of Feeling’s influence on the results appears more pronounced. A broader Field of Feeling leads to quicker decision times when at the reference angle. These outcomes shed light on the feasibility and effectiveness of ultrasonic friction modulation as a tactile feedback mechanism for enhancing the independence of blind individuals. Furthermore, the successful integration of this technology holds the potential to revolutionize electronic surface haptic devices for a wide range of users.

This research presents a measurement method for a compliant gripper finger, whereby the location of the contact with an object and the exerted grasp force are measured indirectly, instead of directly on the contacting surface. For this purpose, the deformation is measured using strain gauges at two locations on the inside structure of the finger, where high deformations occur. The finger is modeled using a Finite Element Analysis, whereby strain data at the two sensor locations is gathered for a set of different contact locations. Now, by matching the measured data to a modeled scenario, both the actual contact location in this scenario and the accompanying contact force can be determined. For the experimental validation, the compliant finger embedded with the two strain gauges is manufactured and an experimental setup has been built. The results show that the contact location can be inferred from strain measurement and contact force is determined accurately up to order of magnitude of 10^-1 newton. Comparing the force-deformation behavior of the original and the embedded finger, a maximum difference of 6% in actuation force was observed. Hence, the sensing method is useful to indirectly measure contact location and force for a compliant finger in contact with an object, while having a minor influence on the grasping performance of the original design.

Endoscopic instruments are integral components of minimally invasive procedures, widely used for diagnoses and treatment of diseases. When navigating the endoscope, it should experience a minimum of friction, while an increase in friction is beneficial for performing the medical procedure. Friction can be reduced by squeeze film levitation, where air is trapped and pressurized between two surfaces by vibrating one of these surfaces. The squeeze film levitates the two surfaces away from each other, hereby reducing friction. Squeeze film levitation between a rigid curved surface and a soft surface is still poorly understood. Also, a proof of concept of a friction modulation mechanism for endoscopes is not yet available in the research literature. Therefore, this paper describes the design and experimental validation of an ultrasonic vibrating ring that can actively modulate friction by generating a squeeze film. On a steel surface, the friction is reduced considerably. However, on the two soft surfaces described in this paper, the reduction of friction is absent.

Hand-worn haptic systems must be able to produce high-quality haptics while also being lightweight and energy-efficient. In order to meet market expectations, research is being done into novel drivetrains that may be implemented in hand worn devices. This is being pushed forward by the growing demand in the virtual reality sector, which is placing pressure on the development of new wearable force feedback technology. In order to validate a proof of concept, this thesis proposes a novel force feedback drivetrain with a dual actuator setup-a motor and a brake—that is integrated into a tabletop prototype. Using both a motor and a brake will reduce weight and improve the haptic rendering quality relative to each component when considered separately.

To evaluate the presumptive advantages, a theoretical analysis into the suggested hybrid actuation solution is conducted. The analysis comprises of numerous simulations using a model of the hybrid drivetrain's working principle. Additionally, the analysis is employed to investigate and spot any early-stage defects or undesirable behavior. Consequently, a 3D model was created in order to 3D print a functioning prototype in order to apply the theory in a physical version. The prototype is initially used to validate the simulation model and enforce the findings of the theoretical analysis. Force data is measured when using the prototype and in turn is fed into the simulation model to assess whether the output behaviour is consistent with the prototype. Both the model's competence and the prototype's predictability are assessed using the outcomes.

Finally, an experiment is conducted to both asses the mechanical performance and predictability as well as the participant's perception; 2 virtual environments and 3 actuation modes (motor, brake, and hybrid) were cross-examined and each repeated 6 times, for a total of 36 trials. This experiment ultimately assesses the prototypes validity and determines whether the theoretically assumed benefits are present in the prototype as well. Finally, the participant completes a questionnaire in the form of a 5-point Likert scale to determine if the experiment data complies with the users experience.

The theoretical analysis revealed both reliable behavior and potential problems, such as oscillations in feedback force due to rapid switching between actuator activity. However, the cause of this behaviour was identified and anticipated to be less pronounced during use of the prototype. The prototype was successfully designed and produced, and a comparison to the model revealed consistent findings and, thus, predictable behavior. However, the model occasionally miscalculated the velocity. The experiment also shows that the hybrid drivetrain approach is promising and outperforms the state of the art both in mechanical prowess as well as physical fidelity when providing haptic feedback; the motor fails to render rigid objects and the brake cannot render spring-like objects, while the hybrid approach can render both successfully.

The thesis demonstrates that additional investigation into the suggested drivetrain is supported, despite some obvious limitations. When compared to equally powerful DC motors, the hybrid technique, as employed in the prototype, is capable of portraying the largest variety of haptics, including hard walls, impacts, and stiffness while potentially conserving weight.

Deformable Object Manipulation (DOM) is an important field of research as it contributes to practical tasks such as cloth handling, cable routing, surgical operation etc. The sensing in DOM is now considered as one of the major challenges in robotics due to the complex dynamics and high degree of freedom of deformable objects. One challenge is to find a suitable representation with low dimensionality and reliable accuracy. The aim of this thesis to develop an algorithm to represent the state of the deformable objects like cloth in low-dimensional vectors, together with a framework based on visual servoing to flatten cloth-like objects. We present a novel pipeline for cloth flattening, which determines a stretching direction (in 2D vector) and an operation point for the robot to removes the wrinkles. The performance of the perception algorithm is validated in simulation and real-world experiment. The whole framework is evaluated in the real-world experiment, which is compared with a human operator. The results show that our framework efficiently determines the direction of wrinkles on the cloth in the simulation as well as the real robot experiment. Besides, the proposed framework has a good performance close to that of a human operator in terms of cloth flattening tasks.

With robotics rapidly expanding towards new user-oriented applications, such as agriculture, households, and classrooms, new tasks and new requirements arise. One of the ongoing and unsolved problems that comes with the unpredictable new environments robots find themselves in, is soft object manipulation. Without assuming the handled object to be rigid, its behavior under forces is no longer known: it could break, bend, plastically deform, or be crushed. In
this paper, we propose a method for the identification of the deformation model of a soft object. We consider a bimanual robotic system manipulating a deformable object with the intention of controlling the object’s shape. Since the object’s deformation parameters are not known in advance, we propose
a learning algorithm for their identification, and we specifically focus on learning the stiffness distribution along the object. By using a state space model based on modes of curvature, rather than a discrete Cartesian state space, we are able to learn the stiffness distribution of the deformable beam with only a single
experiment. Then, we prove that the proposed method provides full control over the shape of the beam by performing a control task in simulation. Given the promising accuracy of the method, this work provides a solid foundation for future work in the direction of the fast identification of deformation parameters.

Conventional steering systems in passenger vehicles have a mechanically fixed steering ratio. The steering sensitivity, defined as the amount of vehicle response to the driver's steering wheel input, remains fixed with changing road environments. Research has shown that driving comfort and safety can be improved when the vehicle's steering sensitivity is adapted to the road curvature profile. Current vehicle models can adapt the vehicle's steering sensitivity based on vehicle's speed and driver's steering wheel angle (i.e variable gear-ratio systems), or on individual selection of driving mode (i.e sport, comfort). It is hypothesised that adaptation of the steering sensitivity based on frequency measures of individual drivers' steering behaviour could improve driving comfort and safety. In a fixed-base driving simulator experiment involving 24 participants, real-time adaptation of steering wheel sensitivity based on individual drivers' steering behaviour was compared to three different fixed steering sensitivity settings on a road with changing road curvature. Here I show that intermittent switching frequency in drivers' steering movements can be used to adapt the vehicle's steering response to a varying road curvature. Significant differences in intermittent switching were found between different road curvature sections and between different steering sensitivity settings. Driver's positional control and comfort ratings did not significantly increase with the steering sensitivity adaptation strategy.

In-Wheel Motor (IWM) vehicle design introduces a lot of benefits for manufacturers. However, it also decreases the ride comfort in the mid-range of perceivable frequencies. The Unsprung Negative Skyhook (UNS) damper control method offers ride comfort improvement in the same frequency range but has its limitations. This thesis proposes two control methods with the aim of maintaining the benefits of the UNS while eliminating the drawbacks. One method is based on a Frequency-range selector (FRS) used in semi-active control. This method allows for a simple but crude frequency estimation by using single sensor information. The second method uses a Short-Time Fourier Transform (STFT) frequency estimator to determine the instantaneous frequency of the vibration. Depending on the vibration frequency, the controllers switch between Skyhook and UNS control to improve overall behaviour. The proposed control methods, as well as state-of-the-art control methods, are evaluated using quarter car and full vehicle simulations. For full vehicle simulations, the models are implemented in IPG CarMaker for realistic dynamic behaviour. Road profiles are obtained from the Gerotek Testing Facility for realistic inputs. Both proposed control methods show improvements for quarter car simulations. For full vehicle simulations, the FRS control method is not able to replicate these improvements. The STFT control method does achieve improvements for all simulations but is limited by its governing models. Finally, suggestions are proposed to further improve the effectiveness of the mixed control method.

Objectives – Over the past decades, more and more cardiac diseases have been treated in interventional cardiology. Catheters are generally used to access the heart through the blood vessels. The previously developed steerable Sigma catheter at Delft University of Technology, tackles cable related challenges of conventional mechanically controlled catheters by an improved tip and shaft design. With its two finger-controlled joysticks, the handle allows full actuation of the four degrees of freedom catheter tip. However, this input control method is not specifically designed for optimal user experience. Therefore, the aim of this research is to design an input control method for the Sigma catheter tip and shaft design to improve task performance while reducing workload for the interventionist. Methods – A theoretical framework was composed and analysed to form design requirements. After detailing the functional and geometrical design, a functional prototype, the Epsilon catheter, was fabricated. To evaluate the proposed control method, an experimental setup was prepared and the control method of both catheters were compared. Six participants were asked to conduct the task, which consisted of contacting targets with the catheter end-point. Target-to-target times were measured and a self-report questionnaire was conducted. Results – The theoretical analysis was divided in the interventional environment, the interventionist who controls the catheter, and the instrumentation. A functional design was made, including catheter control through combining multiple fingers and the wrist using positive input-output coupling. The geometrical design achieved these functionalities through bending flexures and a 180° bended shaft. Data analysis of the experiment showed differences in target-to-target times and self-reported measures. Conclusion – The Epsilon prototype showed to fulfil on the requirements in a functionality test. The prototype allows steering the catheter tip in five degrees of freedom, single-handed in a handheld design. In the experimental setup, participants using the control method of the Epsilon catheter, performed the targeting task faster than using the Sigma catheter with reduced workload. Significance – Allowing the interventionist to control all manoeuvrability of the catheter tip single handed, may change the operational procedure during interventional cardiology. A single interventionist could perform extended treatment using two individually controlled multi-steerable catheters. Further developments will be towards design optimisations to further improve user experience and evaluation of the fifth degree of freedom.

Amyotrophic lateral sclerosis (ALS) is themost frequent form of motor neuron diseases (MND). This neurodegenerativedisease progresses relentlessly quick. The characteristic feature of ALS is theconcurrent degeneration of the upper and lower motoneurons (UMN & LMN) inthe central and peripheral nervous system. Symptomatic behavior in ALS is theresult of complex symptom interplay, as well as symptom counteraction. Therefore,adequate examination of motor function in ALS requires an examination techniquethat quantifies disease symptoms at their origin, rather than at their point ofexpression. The goal of this study was to quantify and explore the effect ofALS on intrinsic and reflexive properties of the limbs of the patients underpassive and active conditions. To the best of our knowledge, this study was thefirst to assess a MND within this particular framework. A group of10 ALS patients and 9 controls were recruited for participation in an extensiveprotocol, comprising of several motor tasks and maximal voluntary contractionmeasurements. The tasks were performed on a single-axis wrist manipulator,which produced multisine torque perturbations. A linear system identificationand parameter estimation procedure was implemented to estimate the parametersof a neuromuscular model with 5 task-dependent (2 intrinsic, 3 reflexive) and 8task-independent parameters. Allparticipants were able to fully comply with the study protocol and indicatedthat the effort required for the tasks was easily maintained. Variance of theintrinsic parameters was generally increased in the patient group, with atendency towards a reduced median. The median of the reflexive parameter musclespindle position dependence was significantly increased in ALS patients during arelax task. Additionally, reflexive and intrinsic parameters of individual patientswere frequently found to be responsive to the patients respective clinicalstate. Muscle stiffness during the relax task was strongly correlated to thesummed average EMG in ALS patients (r = 0.75, p = 0.013). During active tasks,three main control strategies were derived from the intrinsic and reflexiveparameters in patients. We showthat our study protocol is viable for examination of ALS patients within alarge range of physical capacity. The use of quantitative parameters allowed usto disentangle fundamentally overlapping UMN and LMN symptoms. The derivedparameters were shown to enhance clinical scores within their respective clinicaldefinitions. Lastly, our results offer new insights beyond the current clinicalknowledge of motor function under active conditions in ALS.