Amir Degani

Percutaneous Intrapericardial Interventions Using a Highly Articulated Robotic Probe

In order to overcome the limitations of currently available assistive technologies for minimally invasive surgery (MIS), we have developed a novel highly articulated robotic probe (HARP) that can exploit its snake-like structure to navigate in a confined anatomical environment while minimally interacting with the environment along its path. We believe that for procedures involving epicardial interventions on the beating heart, cardiac MIS can be effectively realized with the HARP, entering the pericardial cavity through a subxiphoid port, reaching remote intrapericardial locations on the epicardium without causing hemodynamic and electrophysiologic interference and delivering therapeutic interventions under the direct control of the surgeon

Highly articulated robotic probe for minimally invasive surgery

We have developed a novel highly articulated robotic probe (HARP) that can thread through tightly packed volumes without disturbing the surrounding tissues and organs. We use cardiac surgery as the focal application of this work. As such, we have designed the HARP to enter the pericardial cavity through a subxiphoid port. The surgeon can effectively reach remote intrapericardial locations on the epicardium and deliver therapeutic interventions under direct control. Our device differs from others in that we use conventional actuation and still have great maneuverability. We have performed proof-of-concept clinical experiments to give us preliminary validation of the ideas presented here.

On the Mechanics of Functional Asymmetry in Bipedal Walking

This paper uses two symmetrical models, the passive compass-gait biped and a five-link 3-D biped, to computationally investigate the cause and function of gait asymmetry. We show that for a range of slope angles during passive 2-D walking and mass distributions during controlled 3-D walking, these models have asymmetric walking patterns between the left and right legs due to the phenomenon of spontaneous symmetry-breaking. In both cases a stable asymmetric family of gaits emerges from a symmetric family of gaits as the total energy increases (e.g., fast speeds). The ground reaction forces of each leg reflect different roles, roughly corresponding to support, propulsion, and motion control as proposed by the hypothesis of functional asymmetry in able-bodied human walking. These results suggest that body mechanics, independent of neurophysiological mechanisms such as leg dominance, may contribute to able-bodied gait asymmetry.

A dynamic single actuator vertical climbing robot

A climbing robot mechanism is introduced, which uses dynamic movements to climb between two parallel vertical walls. This robot relies on its own internal dynamic motions to gain height, unlike previous mechanisms which are quasi- static. One benefit of dynamics is that it allows climbing with only a single actuated degree of freedom. We show with analysis, simulations and experiments that this dynamic robot is capable of climbing vertically between parallel walls. We introduce simplifications that enable us to obtain closed form approximations of the robot motion. Furthermore, this provides us with some design considerations and insights into the mechanisms ability to climb.

DSAC - Dynamic, Single Actuated Climber: Local stability and bifurcations

This paper investigates a novel mechanism, called DSAC for Dynamic, Single Actuated Climber, which propels itself upwards by oscillating its leg in a symmetric fashion using a single actuator. This mechanism achieves dynamic, vertical motion while retaining simplicity in design and control. We explore the local orbital stability of the DSAC mechanism. We use the Poincaré map method with a well chosen Poincaré section to simplify the problem by reducing the dimension of the Poincaré map to 3-dimensions. We find the stable regions while varying the controls input and some of the mechanisms parameters. Moreover, in response to a continuous change in a parameter of the mechanism, the symmetric and steady stable gait of the mechanism gradually evolves through a regime of period doubling bifurcations.

A novel highly articulated robotic surgical system for epicardial ablation

We have developed a novel, highly articulated robotic surgical system to enable minimally invasive intrapericardial interventions through a subxiphoid approach and have performed preliminary tests of epicardial left atrial ablation in porcine (N = 3) and human cadaver (N = 2) preparations. In this study, the novel highly articulated robotic surgical system successfully provided safe epicardial ablations to the left atrium in porcine beating heart models via a subxiphoid approach. We have also performed complex guidance of the robot and subsequent ablation in a cadaveric preparation for successful pulmonary vein isolation.

The ParkourBot - a dynamic BowLeg climbing robot

The ParkourBot is an efficient and dynamic climbing robot. The robot comprises two springy legs connected to a body. Leg angle and spring tension are independently controlled. The robot climbs between two parallel walls by leaping from one wall to the other. During flight, the robot stores elastic energy in its springy legs and automatically releases the energy to “kick off” the wall during touch down. This paper elaborates on the mechanical design of the ParkourBot. We use a simple SLIP model to simulate the ParkourBot motion and stability. Finally, we detail experimental results, from open-loop climbing motions to closed-loop stabilization of climbing height in a planar, reduced gravity environment.

The basic mechanics of bipedal walking lead to asymmetric behavior

This paper computationally investigates whether gait asymmetries can be attributed in part to basic bipedal mechanics independent of motor control. Using a symmetrical rigid-body model known as the compass-gait biped, we show that changes in environmental or physiological parameters can facilitate asymmetry in gait kinetics at fast walking speeds. In the environmental case, the asymmetric family of high-speed gaits is in fact more stable than the symmetric family of low-speed gaits. These simulations suggest that lower extremity mechanics might play a direct role in functional and pathological asymmetries reported in human walking, where velocity may be a common variable in the emergence and growth of asymmetry.

Design and Open-Loop Control of the ParkourBot, a Dynamic Climbing Robot

The ParkourBot climbs in a planar reduced-gravity vertical chute by leaping back and forth between the chutes two parallel walls. The ParkourBot is comprised of a body with two springy legs and its controls consist of leg angles at touchdown and the energy stored in them. During flight, the robot stores elastic potential energy in its springy legs and then converts this potential energy in to kinetic energy at touchdown, when it “kicks off” a wall. This paper describes the ParkourBots mechanical design, modeling, and open-loop climbing experiments. The mechanical design makes use of the BowLeg, previously used for hopping on a flat ground. We introduce two models of the BowLeg ParkourBot: one is based on a nonzero stance duration using the spring-loaded inverted pendulum model, and the other is a simplified model (the simplest parkour model, or SPM) obtained as the leg stiffness approaches infinity and the stance time approaches zero. The SPM approximation provides the advantage of closed-form calculations. Finally, predictions of the models are validated by experiments in open-loop climbing in a reduced-gravity planar environment provided by an air table.

Graphical singularity analysis of planar parallel manipulators

This paper introduces a new approach to identify singularities of planar parallel manipulators (PPMs). This method is based on Maxwells reciprocal figure theory which establishes a duality between self stressed frameworks and reciprocal figures, which are abstract dual representations of frameworks. We use line geometry tools to introduce a new graphical construction called the mechanisms line of action graph (MLG). The MLG is introduced in order to implement Maxwells reciprocal figure theory to mechanisms. We show that the configurations where the MLG has a connected reciprocal figure imply a singularity in the mechanism. This singularity analysis tool is also used to trace the singularity loci of the PPM. Finally, we provide detailed examples of the singularity analysis of two common PPMs; one consists of three limbs with a passive revolute joint, actuated prismatic joint and another passive revolute joint (3-RPR), the other consists of three limbs with three revolute joints, where only the first is actuated (3-RRR)