Patrick Lochmatter

Bio: Patrick Lochmatter is an academic researcher from Swiss Federal Laboratories for Materials Science and Technology. The author has contributed to research in topics: Actuator & Robotic arm. The author has an hindex of 6, co-authored 7 publications receiving 345 citations. Previous affiliations of Patrick Lochmatter include ETH Zurich.

An arm wrestling robot driven by dielectric elastomer actuators

Abstract: The first arm wrestling match between a human arm and a robotic arm driven by electroactive polymers (EAP) was held at the EAPAD conference in 2005. The primary objective was to demonstrate the potential of the EAP actuator technology for applications in the field of robotics and bioengineering. The Swiss Federal Laboratories for Materials Testing and Research (Empa) was one of the three organizations participating in this competition. The robot presented by Empa was driven by a system of rolled dielectric elastomer (DE) actuators. Based on the calculated stress condition in the rolled actuator, a low number of pre-strained DE film wrappings were found to be preferential for achieving the best actuator performance. Because of the limited space inside the robot body, more than 250 rolled actuators with small diameters were arranged in two groups according to the human agonist–antagonist muscle configuration in order to achieve an arm-like bidirectional rotation movement. The robot was powered by a computer-controlled high voltage amplifier. The rotary motion of the arm was activated and deactivated electrically by corresponding actuator groups. The entire development process of the robot is presented in this paper where the design of the DE actuators is of primary interest. Although the robot lost the arm wrestling contest against the human opponent, the DE actuators have demonstrated very promising performance as artificial muscles. The scientific knowledge gained during the development process of the robot has pointed out the challenges to be addressed for future improvement in the performance of rolled dielectric elastomer actuators.

Characterization of dielectric elastomer actuators based on a visco-hyperelastic film model

Abstract: The electromechanical performance of planar dielectric elastomer (DE) actuators is predicted by applying a novel model for the mechanical behavior of visco-hyperelastic films such as VHB 4910 (manufactured by 3M). The electrostatic pressure was introduced in the film thickness direction to adapt the film model to DE actuators. Moreover, the actuator was embedded in an appropriate electrical supply circuit to account for the electrodynamic effects. The simulation of the active expansion of a biaxially prestrained, planar DE actuator configuration showed unstable deformation behavior under long-term activation. For activation voltages exceeding a critical level, the active expansion thus became uncontrolled after some time. The model was also applied to a DE strip actuator configuration under sinusoidal electromechanical excitation. The influence of selected parameters on the overall actuator performance was thereby investigated. While the specific energy density increases with increasing amplitudes of the activation voltage and the stretch ratio, the optimum efficiency is predicted to lie at moderate electromechanical excitations.

Spring roll dielectric elastomer actuators for a portable force feedback glove

Abstract: Miniature spring roll dielectric elastomer actuators for a novel kinematic-free force feedback concept were manufactured and experimentally characterized. The actuators exhibited a maximum blocking force of 7.2 N and a displacement of 5 mm. The theoretical considerations based on the material’s incompressibility were discussed in order to estimate the actuator behavior under blocked-strain activation and free-strain activation. One prototype was built for the demonstration of the proposed force feedback concept.

Design and characterization of shell-like actuators based on soft dielectric electroactive polymers

Abstract: This paper is concerned with shell-like actuators based on soft dielectric EAPs, which can actively execute out-of-plane displacements and thus take specific shapes. The structure of the actuators consists of an array of identical segments, where the pre-strained dielectric films are arranged in an agonist-antagonist configuration. The design of the active segments was optimized based on a hyperelastic model for the dielectric film in order to achieve maximum free deformations and blocking loads under activation. Applying these design criteria, shell-like actuators consisting of several interconnected active segments were realized, which can accomplish uniaxial or biaxial bending deformations. Experimental characterization demonstrated the free deformation potential of the presented concepts.

Arm wrestling robot driven by dielectric elastomer actuators

Abstract: On March 7, 2005, the first arm wrestling match of an EAP robotic arm against a human was held during the EAP-inaction session of the EAPAD conference in San Diego. The primary object was to demonstrate the potential of the EAP technology for applications in the field of robotics and bioengineering. The Swiss Federal Laboratories for Materials Testing and Research (Empa), Switzerland, was one of the three participating organizations in this competition. The presented Empa robot was driven by a system of dielectric elastomer actuators. More than 250 rolled actuators were arranged in two groups according to the human agonist-antagonist operating principle in order to achieve an arm-like rotation movement in both directions. The robot was powered by a computer-controlled high voltage amplifier. The rotary motion of the arm was performed by electrical activation respectively deactivation of the corresponding actuator group.

Advances in dielectric elastomers for actuators and artificial muscles.

Abstract: A number of materials have been explored for their use as artificial muscles Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle-like actuation DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied Materials combining very high energy densities, strains, and efficiencies have been known for some time To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications

Robotic Tentacles with Three‐Dimensional Mobility Based on Flexible Elastomers

Abstract: Soft robotic tentacles that move in three dimensions upon pressurization are fabricated by composing flexible elastomers with different tensile strengths using soft lithographic molding. These actuators are able to grip complex shapes and manipulate delicate objects. Embedding functional components into these actuators (for example, a needle for delivering fluid, a video camera, and a suction cup) extends their capabilities.

Multi-functional dielectric elastomer artificial muscles for soft and smart machines

Abstract: Dielectric elastomer (DE) actuators are popularly referred to as artificial muscles because their impressive actuation strain and speed, low density, compliant nature, and silent operation capture many of the desirable physical properties of muscle. Unlike conventional robots and machines, whose mechanisms and drive systems rapidly become very complex as the number of degrees of freedom increases, groups of DE artificial muscles have the potential to generate rich motions combining many translational and rotational degrees of freedom. These artificial muscle systems can mimic the agonist-antagonist approach found in nature, so that active expansion of one artificial muscle is taken up by passive contraction in the other. They can also vary their stiffness. In addition, they have the ability to produce electricity from movement. But departing from the high stiffness paradigm of electromagnetic motors and gearboxes leads to new control challenges, and for soft machines to be truly dexterous like their biological analogues, they need precise control. Humans control their limbs using sensory feedback from strain sensitive cells embedded in muscle. In DE actuators, deformation is inextricably linked to changes in electrical parameters that include capacitance and resistance, so the state of strain can be inferred by sensing these changes, enabling the closed loop control that is critical for a soft machine. But the increased information processing required for a soft machine can impose a substantial burden on a central controller. The natural solution is to distribute control within the mechanism itself. The octopus arm is an example of a soft actuator with a virtually infinite number of degrees of freedom (DOF). The arm utilizes neural ganglia to process sensory data at the local “arm” level and perform complex tasks. Recent advances in soft electronics such as the piezoresistive dielectric elastomer switch (DES) have the potential to be fully integrated with actuators and sensors. With the DE switch, we can produce logic gates, oscillators, and a memory element, the building blocks for a soft computer, thus bringing us closer to emulating smart living structures like the octopus arm. The goal of future research is to develop fully soft machines that exploit smart actuation networks to gain capabilities formerly reserved to nature, and open new vistas in mechanical engineering.

Electronic Muscles and Skins: A Review of Soft Sensors and Actuators

Abstract: This article reviews several classes of compliant materials that can be utilized to fabricate electronic muscles and skins. Different classes of materials range from compliant conductors, semiconductors, to dielectrics, all of which play a vital and cohesive role in the development of next generation electronics. This paper covers recent advances in the development of new materials, as well as the engineering of well-characterized materials for the repurposing in applications of flexible and stretchable electronics. In addition to compliant materials, this article further discusses the use of these materials for integrated systems to develop soft sensors and actuators. These new materials and new devices pave the way for a new generation of electronics that will change the way we see and interact with our devices for decades to come.