Simon Hauser

JammJoint: A Variable Stiffness Device Based on Granular Jamming for Wearable Joint Support

In robotics, controlling the stiffness of the joints that contribute to the robots’ degree of freedom dictates the adaptability, versatility, and safety of the whole system. We can achieve variable stiffness or impedance in a robotic system purely by the control or by introducing new material or mechanisms to address cases that require innate safety through system compliancy. This paper presents JammJoint, a compliant and flexible wearable robot, which uses jamming of granular media to vary its stiffness. It consists of a silicone sleeve with hollow sections that are filled with cubic rubber granules and subjected to different levels of vacuum pressure. Unlike contemporary vacuum-based actuators or systems, JammJoint is wearable, portable, and autonomous: It uses a powerful miniature vacuum pump, a small battery, and bluetooth-enabled electronics. Experiments revolving around bending and torsional stiffness show that the system is able to achieve up to a fourfold increase in spring stiffness. Further measurements of individual variable stiffness structures indicate that for other modes of deformation, including simply supported bending or compression for alternative linear applications, higher changes in stiffness over a factor of seven are possible. These aspects make mobile jamming-based stiffness variation as wearable joint assistance promising for future applications such as rehabilitation after injuries and joint support in challenging working conditions.

Friction and damping of a compliant foot based on granular jamming for legged robots

Moving away from simple foot designs of current quadruped robots towards a more bio-inspired approach, a novel foot design was implemented on the quadruped robot Oncilla. These feet mimic soft paw-pads of dogs and cats with high traction and soft underlying tissue. Consisting of a granular medium enclosed in a flexible membrane, they can be set to different pressure/vacuum conditions. Tests of general properties such as friction force, damping and deformation were completed by proof of concept tests on the robot. These included flat ground locomotion as well as ascending a slope with different inclination. Comparison tests with the previous feet were performed as well, showing that the new feet have a high friction and strong damping properties. Additionally, the speed of flat ground locomotion is comparable to the maximum speed of the robot with the previous feet while retaining the desired trotting gait. These are promising aspects for legged locomotion. The jamming of granular media previously has been used to create a universal gripper which in the future also opens up opportunities to use the feet both in locomotion and simple object manipulation (although the manipulation is not tested here).

Robotic Invention: Challenges and Perspectives for Model-Free Design Optimization of Dynamic Locomotion Robots

To improve a robot’s performance at a given task, or to respond to changing requirements, shape adaptation can be beneficial. To efficiently explore complex behaviors, diverse morphologies must be generated and implemented. For continuous and autonomous design optimization, the robot has furthermore to be able to assess its own performance and in turn generate and implement adapted morphological designs. Here, we present the morphological adaptation of physical robotic agents to a locomotion task. The robots are automatically assembled by a robotic manipulator from elementary modules and the assembly process of each agent is encoded in a genotype. The genotypes of a robot population are optimized using an evolutionary algorithm based on real-world performance feedback. In the experiments, 500 genotypes were evaluated. To develop rich behavioral diversity, shape variations are beneficial. Analysis of the results highlights the influence of the fabrication constraints on shape diversity, which impose limitations especially for larger structures.

Compliant universal grippers as adaptive feet in legged robots

ABSTRACT This work investigates the usage of compliant universal grippers as a novel foot design for legged locomotion. The method of jamming of granular media in the universal grippers is characterized by having two distinct states: a soft, fluid-like state which in locomotion can be used to damp impact forces and enable passive shape adaptation especially on rough terrain, and a hard, solid-like state that is more suited to transmit propulsion forces. We propose a system that actively uses and switches between both states of a foot design based on granular jamming and detail the implementation on a quadruped robotic platform. The mechanism is inspired by the stiffness varying function of the tarsal bones in a human foot, and our aim is to understand how the change of foot stiffness can be used to improve the locomotion performance of legged robots. Using the same open loop trot gait in all experiments, it is shown that a fast state transition enables the robot to profit from both states, leading to more uniform foot placement patterns also on rough terrain compared to other tested feet. This results in overall faster gaits and even enables the robot to climb steeper inclined surfaces. GRAPHICAL ABSTRACT

Effects of passive and active joint compliance in quadrupedal locomotion

ABSTRACT Compliance of the body has a crucial role on locomotion performance. The levels and the distribution of compliance should be well tuned to obtain efficient gait. The leg stiffness changes significantly even during different phases of a single gait cycle. This paper presents an experimental study on different passive and active limb compliance configurations. Each configuration is tested on flat, rough and inclined-rough surfaces, to analyze locomotion performance in diverse conditions. As the active compliance mechanism, Tegotae-based control is selected. Even though active compliance is not its primary use, we show that the Tegotae rule presents intriguing features that have potential to boost gait performance in various scenarios. GRAPHICAL ABSTRACT

Self-reconfigurable modular robot interface using virtual reality: Arrangement of furniture made out of roombots modules, 2017 26th IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN)

Self-reconfigurable modular robots (SRMR) offer high flexibility in task space by adopting different morphologies for different tasks. Using the same simple module, complex and more capable morphologies can be built. However, increasing the number of modules increases the degrees of freedom (DOF) of the system. Thus, controlling the system as a whole becomes harder. Indeed, even a 10 DOFs system is difficult to consider and manipulate. Intuitive and easy to use interfaces are needed, particularly when modular robots need to interact with humans. In this study we present an interface to assemble desired structures and placement of such structures, with a focus on the assembly process. Roombots modules, a particular SRMR design, are used for the demonstration of the proposed interface. Two non-conventional input/output devices — a head mounted display and hand tracking system — are added to the system to enhance the user experience. Finally, a user study was conducted to evaluate the interface. The results show that most users enjoyed their experience. However, they were not necessarily convinced by the gesture control, most likely for technical reasons.

Active stabilization of a stiff quadruped robot using local feedback, 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

Animal locomotion exhibits all the features of complex non linear systems such as multi-stability, critical fluctuation, limit cycle behavior and chaos. Studying these aspects on real robots has been proved difficult and therefore results mostly rely on the use of computer simulation. Simple control approaches — based on phase oscillators — have been proposed and exhibit several of these features. In this work, we compare two types of controllers: (a) an open loop control approach based on phase oscillators and (b) the Tegotae-based closed loop extension of this controller. The first controller has been shown to exhibit synchronization features between the body and the controller when applied to a quadruped robot with compliant leg structures. In this contribution, we apply both controllers to the locomotion of a stiff quadruped structure. We show that the Tegotae-controller exhibits self-organizing behavior, such as spontaneous gait transition and critical fluctuation. Moreover, it exhibits features such as the ability to stabilize both asymmetric and symmetric morphological changes, despite the lack of compliance in the leg.

Natural user interface for lighting control: Case study on desktop lighting using modular robots

Roombots (RB) are self-reconfigurable modular robots designed to explore physical structure change by robotic reconfiguration and adaptive locomotion on structured grid environments or unstructured environments. The primary goal of RB is to create adaptive furniture. In this study, we propose a novel and user-friendly interface to control position and intensity of a mobile desk light using RB modules. In the proposed method, the user interacts with the RB with only hand/arm gestures. The users arm is tracked with a single Kinect having birds eye view. We demonstrate the effectiveness of the proposed interface in real hardware setup and discuss contributions of it.