Michael R. Tucker

Bio: Michael R. Tucker is an academic researcher from General Electric. The author has contributed to research in topics: Gait (human) & Orthotic device. The author has an hindex of 6, co-authored 14 publications receiving 808 citations. Previous affiliations of Michael R. Tucker include ETH Zurich & Clarkson University.

Control strategies for active lower extremity prosthetics and orthotics: a review

Abstract: Technological advancements have led to the development of numerous wearable robotic devices for the physical assistance and restoration of human locomotion. While many challenges remain with respect to the mechanical design of such devices, it is at least equally challenging and important to develop strategies to control them in concert with the intentions of the user. This work reviews the state-of-the-art techniques for controlling portable active lower limb prosthetic and orthotic (P/O) devices in the context of locomotive activities of daily living (ADL), and considers how these can be interfaced with the user’s sensory-motor control system. This review underscores the practical challenges and opportunities associated with P/O control, which can be used to accelerate future developments in this field. Furthermore, this work provides a classification scheme for the comparison of the various control strategies. As a novel contribution, a general framework for the control of portable gait-assistance devices is proposed. This framework accounts for the physical and informatic interactions between the controller, the user, the environment, and the mechanical device itself. Such a treatment of P/Os – not as independent devices, but as actors within an ecosystem – is suggested to be necessary to structure the next generation of intelligent and multifunctional controllers. Each element of the proposed framework is discussed with respect to the role that it plays in the assistance of locomotion, along with how its states can be sensed as inputs to the controller. The reviewed controllers are shown to fit within different levels of a hierarchical scheme, which loosely resembles the structure and functionality of the nominal human central nervous system (CNS). Active and passive safety mechanisms are considered to be central aspects underlying all of P/O design and control, and are shown to be critical for regulatory approval of such devices for real-world use. The works discussed herein provide evidence that, while we are getting ever closer, significant challenges still exist for the development of controllers for portable powered P/O devices that can seamlessly integrate with the user’s neuromusculoskeletal system and are practical for use in locomotive ADL.

Design of a wearable perturbator for human knee impedance estimation during gait

Abstract: Mechanical impedance modulation is the key to natural, stable and efficient human locomotion. An improved understanding of this mechanism is necessary for the development of the next generation of intelligent prosthetic and orthotic devices. This paper documents the design methodologies that were employed to realize a knee perturbator that can experimentally estimate human knee impedance during gait through the application of angular velocity perturbations. The proposed experiment requires a light, transparent, wearable, and remotely actuated device that closely follows the movement of the biological joint. A genetic algorithm was used to design a polycentric hinge whose instantaneous center of rotation is optimized to be kinematically compatible with the human knee. A wafer disc clutch was designed to switch between a high transparency passive mode and a high impedance actuated mode. A remote actuation and transmission scheme was designed to enable high power output perturbations while minimizing the device's mass. Position and torque sensors were designed for device control and to provide data for post-processing and joint impedance estimation. Pending the fabrication and mechanical testing of the device, we expect this knee perturbator to be a valuable tool for experimental investigation of locomotive joint impedance modulation.

Design and Characterization of an Exoskeleton for Perturbing the Knee During Gait

Abstract: Objective: An improved understanding of mechanical impedance modulation in human joints would provide insights about the neuromechanics underlying functional movements. Experimental estimation of impedance requires specialized tools with highly reproducible perturbation dynamics and reliable measurement capabilities. This paper presents the design and mechanical characterization of the ETH Knee Perturbator: an actuated exoskeleton for perturbing the knee during gait. Methods: A novel wearable perturbation device was developed based on specific experimental objectives. Bench-top tests validated the device's torque limiting capability and characterized the time delays of the on-board clutch. Further tests demonstrated the device's ability to perform system identification on passive loads with static initial conditions. Finally, the ability of the device to consistently perturb human gait was evaluated through a pilot study on three unimpaired subjects. Results: The ETH Knee Perturbator is capable of identifying mass-spring systems within 15% accuracy, accounting for over 95% of the variance in the observed torque in 10 out of 16 cases. Five-degree extension and flexion perturbations were executed on human subjects with an onset timing precision of 2.52% of swing phase duration and a rise time of 36.5 ms. Conclusion: The ETH Knee Perturbator can deliver safe, precisely timed, and controlled perturbations, which is a prerequisite for the estimation of knee joint impedance during gait. Significance: Tools such as this can enhance models of neuromuscular control, which may improve rehabilitative outcomes following impairments affecting gait and advance the design and control of assistive devices.

Mechanical damping with electrical regeneration for a powered transfemoral prosthesis

Abstract: This paper presents the analytical model of a DC-motor actuated active-knee transfemoral prosthesis operating within the mechanically dissipative but electrically regenerative region of the knee actuator's performance space. A switching-based control scheme is developed that enables damping control within the limb's regenerative region of operation. This control approach allows the limb to realize bounded mechanical dissipation using a strictly passive means, while at the same time generating electrical power to augment the limb's power requirements in active modes of operation. Experimental characterizations of the performance and regenerative efficiency of the switching-based controller indicate that the passive switching controller can provide damping modulation, but at the expense of decreased efficiencies of regeneration as compared to the theoretical projections of the actuator model.

Physical Student–Robot Interaction With the ETHZ Haptic Paddle

Abstract: Haptic paddles-low-cost one-degree-of-freedom force feedback devices-have been used with great success at several universities throughout the US to teach the basic concepts of dynamic systems and physical human-robot interaction (pHRI) to students The ETHZ haptic paddle was developed for a new pHRI course offered in the undergraduate Mechatronics Focus track of the Mechanical Engineering curriculum at ETH Zurich, Switzerland Twenty students engaged in this 2-h weekly lecture over the 14 weeks of the Autumn 2011 semester, complemented by a weekly 2-h laboratory session with the ETHZ haptic paddle In pairs, students worked through three common sets of experiments before embarking on a specialization project that investigated one of several advanced topics such as impedance control with force feedback, admittance control, the effect of velocity estimation on stability, or electromyographic control For these projects, students received additional hardware, including force sensors, electrooptical encoders or high-performance data acquisition cards The learning objectives were developed in the context of an accompanying faculty development program at ETH Zurich; a set of interactive sequences and the oral exam were explicitly aligned to these learning objectives The outcomes of the specialization project presentations and oral exams, and a student evaluation of the course, demonstrated that the ETHZ haptic paddle is a valuable tool that allows students to quite literally grasp abstract principles such as mechanical impedance, passivity, and human factors and helps students create a tangible link between theory and practice in the highly interdisciplinary field of pHRI

Control strategies for active lower extremity prosthetics and orthotics: a review

Abstract: Technological advancements have led to the development of numerous wearable robotic devices for the physical assistance and restoration of human locomotion. While many challenges remain with respect to the mechanical design of such devices, it is at least equally challenging and important to develop strategies to control them in concert with the intentions of the user. This work reviews the state-of-the-art techniques for controlling portable active lower limb prosthetic and orthotic (P/O) devices in the context of locomotive activities of daily living (ADL), and considers how these can be interfaced with the user’s sensory-motor control system. This review underscores the practical challenges and opportunities associated with P/O control, which can be used to accelerate future developments in this field. Furthermore, this work provides a classification scheme for the comparison of the various control strategies. As a novel contribution, a general framework for the control of portable gait-assistance devices is proposed. This framework accounts for the physical and informatic interactions between the controller, the user, the environment, and the mechanical device itself. Such a treatment of P/Os – not as independent devices, but as actors within an ecosystem – is suggested to be necessary to structure the next generation of intelligent and multifunctional controllers. Each element of the proposed framework is discussed with respect to the role that it plays in the assistance of locomotion, along with how its states can be sensed as inputs to the controller. The reviewed controllers are shown to fit within different levels of a hierarchical scheme, which loosely resembles the structure and functionality of the nominal human central nervous system (CNS). Active and passive safety mechanisms are considered to be central aspects underlying all of P/O design and control, and are shown to be critical for regulatory approval of such devices for real-world use. The works discussed herein provide evidence that, while we are getting ever closer, significant challenges still exist for the development of controllers for portable powered P/O devices that can seamlessly integrate with the user’s neuromusculoskeletal system and are practical for use in locomotive ADL.

State of the Art and Future Directions for Lower Limb Robotic Exoskeletons

Abstract: Research on robotic exoskeletons has rapidly expanded over the previous decade. Advances in robotic hardware and energy supplies have enabled viable prototypes for human testing. This review paper describes current lower limb robotic exoskeletons, with specific regard to common trends in the field. The preponderance of published literature lacks rigorous quantitative evaluations of exoskeleton performance, making it difficult to determine the disadvantages and drawbacks of many of the devices. We analyzed common approaches in exoskeleton design and the convergence, or lack thereof, with certain technologies. We focused on actuators, sensors, energy sources, materials, and control strategies. One of the largest hurdles to be overcome in exoskeleton research is the user interface and control. More intuitive and flexible user interfaces are needed to increase the success of robotic exoskeletons. In the last section, we discuss promising future solutions to the major hurdles in exoskeleton control. A number of emerging technologies could deliver substantial advantages to existing and future exoskeleton designs. We conclude with a listing of the advantages and disadvantages of the emerging technologies and discuss possible futures for the field.

Brain-Machine Interfaces: From Basic Science to Neuroprostheses and Neurorehabilitation

Abstract: Brain-machine interfaces (BMIs) combine methods, approaches, and concepts derived from neurophysiology, computer science, and engineering in an effort to establish real-time bidirectional links bet...

The exoskeleton expansion: improving walking and running economy

Abstract: Since the early 2000s, researchers have been trying to develop lower-limb exoskeletons that augment human mobility by reducing the metabolic cost of walking and running versus without a device. In 2013, researchers finally broke this ‘metabolic cost barrier’. We analyzed the literature through December 2019, and identified 23 studies that demonstrate exoskeleton designs that improved human walking and running economy beyond capable without a device. Here, we reviewed these studies and highlighted key innovations and techniques that enabled these devices to surpass the metabolic cost barrier and steadily improve user walking and running economy from 2013 to nearly 2020. These studies include, physiologically-informed targeting of lower-limb joints; use of off-board actuators to rapidly prototype exoskeleton controllers; mechatronic designs of both active and passive systems; and a renewed focus on human-exoskeleton interface design. Lastly, we highlight emerging trends that we anticipate will further augment wearable-device performance and pose the next grand challenges facing exoskeleton technology for augmenting human mobility.