—It has been shown that people can learn to perform a variety of motor tasks in novel dynamic env... more —It has been shown that people can learn to perform a variety of motor tasks in novel dynamic environments without visual feedback, highlighting the importance of proprioceptive feedback in motor learning. However, our results show that it is possible to learn a viscous curl force field without proprioceptive error to drive adaptation, by providing visual information about the position error. Subjects performed reaching movements in a constraining channel created by a robotic interface. The force that subjects applied against the haptic channel was used to predict the unconstrained hand trajectory under a viscous curl force field. This trajectory was provided as visual feedback to the subjects during movement (virtual dynamics). Subjects were able to use this visual information (discrepant with proprioception) and gradually learned to compensate for the virtual dynamics. Unconstrained catch trials, performed without the haptic channel after learning the virtual dynamics, exhibited similar trajectories to those of subjects who learned to move in the force field in the unconstrained environment. Our results demonstrate that the internal model of the external dynamics that was formed through learning without proprioceptive error was accurate enough to allow compensation for the force field in the unconstrained environment. They suggest a method to overcome limitations in learning resulting from mechanical constraints of robotic trainers by providing suitable visual feedback, potentially enabling efficient physical training and rehabilitation using simple robotic devices with few degrees-of-freedom.
Haptic paddles — low-cost one-degree-of-freedom force feedback devices — have been used with grea... more Haptic paddles — low-cost one-degree-of-freedom force feedback devices — have been used with great success at several universities throughout the United States 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 two-hour weekly lecture over the 14 weeks of the autumn 2011 semester, complemented by a weekly two-hour 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, electro-optical 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.
We are developing haptic interfaces compatible with functional magnetic resonance imaging (fMRI) ... more We are developing haptic interfaces compatible with functional magnetic resonance imaging (fMRI) to study the brain mechanisms of motor control in humans. This paper describes the different phases of our project, examines the constraints and presents possible solutions. The constraints imposed by the harsh yet sensitive MR environment as well as the smooth and safe control required for interaction with human motion demand a novel robotic technology. Our concept is based on a hydrostatic master-slave system used to power the robot near the scanner from outside the shielded MR room. Force/torque and position sensors measure the deflection of an elastic polymer probe via light intensity measurement over fiber optics, thus allowing all electronic components to be placed outside the MR room. This concept was validated through two interfaces able to provide force and motion feedback simultaneously with imaging.
Magnetically compatible robots are required to develop haptic interfaces for neuroscience studies... more Magnetically compatible robots are required to develop haptic interfaces for neuroscience studies and MRI guided robots for minimally invasive interventions. This paper introduces an MR compatible master slave concept using a hydraulic transmission, and presents an operational robot able to work within an MRI/fMRI scanner and acquire images continuously during motion. It describes a magnetically inert actuator using a direct drive to power the hydraulic circuitry and a modular set of position and force/torque sensors that we have developed. These were integrated into a haptic interface prototype with on rotary degree of freedom, which can be used in conjuction with an fMRI. The MR compatibility was confirmed experimentally, and the performances show a manipulation accuracy of a few micrometers over a range of several centimeters, and forces up to several thousand Newton.
This paper investigates robot-assisted rehabilitation after stroke using the haptic knob, a 2 deg... more This paper investigates robot-assisted rehabilitation after stroke using the haptic knob, a 2 degree-of-freedom end-effector based robotic device to train grasping and wrist pronation/supination. Nine chronic stroke subjects trained over a period of 6 weeks, with 3 one-hour sessions of robot-assisted therapy per week, consisting of two exercises requiring active participation promoted by therapeutic games. Results of standard clinical assessments demonstrate the positive effects of robot-assisted therapy with the haptic knob. Subjects improved by a mean of 4.3 points in the Fugl-Meyer assessment scale, together with a decrease in hand impairments such as abnormal muscle tone frequently observed in stroke subjects. Significant improvements were also observed in motor function of the upper arm as a result of the robot-assisted therapy, suggesting homogeneous improvement of upper limb function as a result of distal training.
The strong impairment of motor functions in stroke survivors affects daily activities such as eat... more The strong impairment of motor functions in stroke survivors affects daily activities such as eating, manipulating objects or writing. Our goal is to induce long lasting improvements in such tasks by having patients perform systematic exercises using haptic interfaces. This paper describes a novel two-degrees-of-freedom interface which we have developed to help stroke patients gradually recover the ability to open and close the hand and manipulate knobs. Different solutions are studied and a design consisting of two parallelogram structures interacting with the fingers is proposed. The mechanical design offers the possibility to adapt the interface to various hand sizes and finger orientations, and to right or left-handed subjects. Design kinematics as well as actuation and system control are described. Several knobs are proposed to interact with patients, especially a cone mechanism to train a complete opening movement from a strongly contracted and closed hand to a large opened position. The interaction force with the subject is measured over four force sensors located close to the output of the interface. A preliminary study has been performed to evaluate the performances of the haptic interface
—It has been shown that people can learn to perform a variety of motor tasks in novel dynamic env... more —It has been shown that people can learn to perform a variety of motor tasks in novel dynamic environments without visual feedback, highlighting the importance of proprioceptive feedback in motor learning. However, our results show that it is possible to learn a viscous curl force field without proprioceptive error to drive adaptation, by providing visual information about the position error. Subjects performed reaching movements in a constraining channel created by a robotic interface. The force that subjects applied against the haptic channel was used to predict the unconstrained hand trajectory under a viscous curl force field. This trajectory was provided as visual feedback to the subjects during movement (virtual dynamics). Subjects were able to use this visual information (discrepant with proprioception) and gradually learned to compensate for the virtual dynamics. Unconstrained catch trials, performed without the haptic channel after learning the virtual dynamics, exhibited similar trajectories to those of subjects who learned to move in the force field in the unconstrained environment. Our results demonstrate that the internal model of the external dynamics that was formed through learning without proprioceptive error was accurate enough to allow compensation for the force field in the unconstrained environment. They suggest a method to overcome limitations in learning resulting from mechanical constraints of robotic trainers by providing suitable visual feedback, potentially enabling efficient physical training and rehabilitation using simple robotic devices with few degrees-of-freedom.
Haptic paddles — low-cost one-degree-of-freedom force feedback devices — have been used with grea... more Haptic paddles — low-cost one-degree-of-freedom force feedback devices — have been used with great success at several universities throughout the United States 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 two-hour weekly lecture over the 14 weeks of the autumn 2011 semester, complemented by a weekly two-hour 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, electro-optical 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.
We are developing haptic interfaces compatible with functional magnetic resonance imaging (fMRI) ... more We are developing haptic interfaces compatible with functional magnetic resonance imaging (fMRI) to study the brain mechanisms of motor control in humans. This paper describes the different phases of our project, examines the constraints and presents possible solutions. The constraints imposed by the harsh yet sensitive MR environment as well as the smooth and safe control required for interaction with human motion demand a novel robotic technology. Our concept is based on a hydrostatic master-slave system used to power the robot near the scanner from outside the shielded MR room. Force/torque and position sensors measure the deflection of an elastic polymer probe via light intensity measurement over fiber optics, thus allowing all electronic components to be placed outside the MR room. This concept was validated through two interfaces able to provide force and motion feedback simultaneously with imaging.
Magnetically compatible robots are required to develop haptic interfaces for neuroscience studies... more Magnetically compatible robots are required to develop haptic interfaces for neuroscience studies and MRI guided robots for minimally invasive interventions. This paper introduces an MR compatible master slave concept using a hydraulic transmission, and presents an operational robot able to work within an MRI/fMRI scanner and acquire images continuously during motion. It describes a magnetically inert actuator using a direct drive to power the hydraulic circuitry and a modular set of position and force/torque sensors that we have developed. These were integrated into a haptic interface prototype with on rotary degree of freedom, which can be used in conjuction with an fMRI. The MR compatibility was confirmed experimentally, and the performances show a manipulation accuracy of a few micrometers over a range of several centimeters, and forces up to several thousand Newton.
This paper investigates robot-assisted rehabilitation after stroke using the haptic knob, a 2 deg... more This paper investigates robot-assisted rehabilitation after stroke using the haptic knob, a 2 degree-of-freedom end-effector based robotic device to train grasping and wrist pronation/supination. Nine chronic stroke subjects trained over a period of 6 weeks, with 3 one-hour sessions of robot-assisted therapy per week, consisting of two exercises requiring active participation promoted by therapeutic games. Results of standard clinical assessments demonstrate the positive effects of robot-assisted therapy with the haptic knob. Subjects improved by a mean of 4.3 points in the Fugl-Meyer assessment scale, together with a decrease in hand impairments such as abnormal muscle tone frequently observed in stroke subjects. Significant improvements were also observed in motor function of the upper arm as a result of the robot-assisted therapy, suggesting homogeneous improvement of upper limb function as a result of distal training.
The strong impairment of motor functions in stroke survivors affects daily activities such as eat... more The strong impairment of motor functions in stroke survivors affects daily activities such as eating, manipulating objects or writing. Our goal is to induce long lasting improvements in such tasks by having patients perform systematic exercises using haptic interfaces. This paper describes a novel two-degrees-of-freedom interface which we have developed to help stroke patients gradually recover the ability to open and close the hand and manipulate knobs. Different solutions are studied and a design consisting of two parallelogram structures interacting with the fingers is proposed. The mechanical design offers the possibility to adapt the interface to various hand sizes and finger orientations, and to right or left-handed subjects. Design kinematics as well as actuation and system control are described. Several knobs are proposed to interact with patients, especially a cone mechanism to train a complete opening movement from a strongly contracted and closed hand to a large opened position. The interaction force with the subject is measured over four force sensors located close to the output of the interface. A preliminary study has been performed to evaluate the performances of the haptic interface
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Papers by Roger Gassert