Yu Ikemoto

A study on wire-wire driven abdominal cavity mobile micro robot

NOTES (Natural Orifice Translumenal Endoscopic Surgery), a recently developed form of minimally invasive surgery, has attracted attention as a new laparoscopic operation. However, manipulation of forceps throughout the surgery continues to be a burden to surgeons. Our previous research focused on designing a model that could carry forceps and a camera through the abdominal cavity. The first prototype, a wire-tube driven micro robot, relied on the action of two suction cups for movement along the peritoneum (abdominal wall). However, the actions required to carry out the turning motions of the first prototype were strongly influenced by the rigidity of the tube. In order to solve this problem, in this study, we proposed a wire-wire driving mechanism for the robot, then developed a simulation model for investigating design and control issues. Based on the investigation, a new prototype was designed to determine the feasibility of the robot. Our results showed the robots potential as a NOTES support device.

Comparing normal walking and compensated walking: their stability and perturbation resistance. A simulation study.

Abstract People usually develop different kinds of compensated gait in response to local function deficits, such as muscle weakness, spasticity in specific muscle groups, or joint stiffness, in order to overcome the falling risk factors. Compensated walking has been analysed empirically in the impaired gait analysis area. However, the compensation could be identified spatially and temporally. The stability and perturbation resistance of compensated walking have not been analysed quantitatively. In this research, a biomimetic human walking simulator was employed to model one individual paraplegic subject with plantarflexor spasticity. The pes equinus was expressed by biasing the outputs of plantarflexor neurons corresponding to the spastic muscles. Then, the compensatory mechanism was explored by adjusting the outputs of the other muscles. It was shown that this approach can be used for quantitative analysis of the spastic gait and compensated walking. Thus, this research can improve the understanding of the behaviour of compensated walking, bringing insights not only for building useful walking assist systems with high safety but also for designing effective rehabilitation interventions.

The roles of CPG phase modulation and reflexive muscular patterns in balance recovery during walking---a simulation study

Most walking assist systems reported are not available for real world environments where frequent perturbations are caused by slips, uneven terrain, slopes and obstacles. It is evident that humans are able to cope with such perturbations with reflexes that cause unconscious, relatively fixed muscular response patterns to perturbations within a short period of time. In our previous study, we showed that artificial reflexes could improve the perturbation resistance for simulated walkers, though the roles of different reflexive mechanisms were not quantitatively clarified. In this study, we focused on the different roles of reflexive muscle responses and the CPG phase modulation mechanism. By proposing and evaluating two stability criteria through a series of simulation experiments, we revealed different roles for two mechanisms in the simulated walkers. These will not only further increase the possibility of realising artificial reflexes for paralysed individuals, but also bring new insights into the field of motor control.

Analyzing of compensated strategy in impaired walking using a humanoid robot

People usually develop different kinds of compensated gait in response to their local function deficits, such as muscle weakness, spasticity in specific muscle groups, or joint stiffness, to overcome the risk of falling-down. Compensated walking in impaired walking has been analyzed empirically in gait analysis area. However, the characteristic of the compensated walking has not been analyzed considering the nervous system. In this research, we employed a bio-mimetic humanoid robot with a neural model to emulate a hemiplegic gait with a deficit in the ankle flexor and the hip extensor. The deficits were expressed by setting a limitation for the outputs of the ankle flexor and decreasing the output of the hip extensor. Then a compensatory mechanism was explored by adjusting the outputs of the other muscles. We showed that, it is possible to use this approach to quantitatively analyze a hemiplegic gait and its compensated walking. Thus, in this research we were able to improve the behavioral understanding of a compensated gait and bring insights that will help build useful walking assistive systems or for designing effective rehabilitation therapies.

An artificial reflex improves the perturbation-resistance of normal and spastic walking - A simulation study -

Walking assist systems should cope with both the external perturbation caused by slips, uneven terrain, slopes, and obstacles, and local function impairment caused by internal factors, like spastic paralysis. It is known that humans are able to cope with these difficulties by different strategies. One is that in the case when external perturbation occurs, especially when the occurrence cannot be predicted or perceived in advance, humans rely on reflexes, which cause unconscious, relatively fixed muscular response patterns to perturbations within a short period of time. Another is that in the case of local function impairment, humans generally develop compensated gait to overcome the falling-down risky factors.

A study on balance maintenance strategies during walking - A simulation study

Walking assist systems should cope with both the external perturbation caused by slips, uneven terrain, slopes, and obstacles, and local function impairment caused by internal factors, like spastic paralysis. It is known that humans are able to cope with these difficulties by different strategies. One is that in the case when external perturbation occurs, especially when the occurrence cannot be predicted or perceived in advance, humans rely on reflexes, which cause unconscious, relatively fixed muscular response patterns to perturbations within a short period of time. Another is that in the case of local function impairment, humans generally develop compensated gait to overcome the falling-down risky factors.

The Roles of CPG Phase Modulation and Reflexive Muscular Patterns in Balance Recovery Reflexive Responses to Perturbation during Walking - A Simulation Study

Most walking assist systems reported are not ready for using in real-world environment, where there are frequent perturbations resulted from slips, uneven terrain, slopes and obstacles. Our ultimate goal is to realize artificial reflexes to real-world walking support systems for those paralyzed people. This goal needs both qualitative and quantitative understanding of human reflexive mechanism. Our approach includes 1. acquiring muscle activity profiles during normal walking and slip-perturbed walking by recording and processing electromyographic (EMG) of several walking-related muscles, in a human gait experiment; 2. developing a central-pattern-generator (CPG) based neuro-musculo-skeletal simulation model; 3. using muscle activity profiles of reflexive muscle responses together with a CPG-phase-modulation mechanism, to construct a rapid responding pathway, and investigating the effects of the pathway on the simulated walker, as well as verifying several hypotheses on the underlying neuro- mechanism. Experiments were performed in a walking simulation model to investigate the roles of the two functional aspects. Results showed that, 1. CPG phase modulation alone could also improve the perturbation resistance on the occurrence of a comparatively small slip perturbation, by interacting with a pre-wired sensory- feedback mechanism; 2. on the occurrence of a big slip- perturbation, together with the CPG phase modulation, the rapid muscular responses could improve the perturbation- resistance and maintain balance for the simulated walker.