M. S. Raghu Prasad

Bio: M. S. Raghu Prasad is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Haptic technology & Fitts's law. The author has an hindex of 5, co-authored 6 publications receiving 59 citations.

Effects of laparoscopic instrument and finger on force perception: a first step towards laparoscopic force-skills training

Abstract: In laparoscopic surgery, no external feedback on the magnitude of the force exerted is available. Hence, surgeons and residents tend to exert excessive force, which leads to tissue trauma. Ability of surgeons and residents to perceive their own force output without external feedback is a critical factor in laparoscopic force-skills training. Additionally, existing methods of laparoscopic training do not effectively train residents and novices on force-skills. Hence, there is growing need for the development of force-based training curriculum. As a first step towards force-based laparoscopic skills training, this study analysed force perception difference between laparoscopic instrument and finger in contralateral bimanual passive probing task. The study compared the isometric force matching performance of novices, residents and surgeons with finger and laparoscopic instrument. Contralateral force matching paradigm was employed to analyse the force perception capability in terms of relative (accuracy), and constant errors in force matching. Force perception of experts was found to be better than novices and residents. Interestingly, laparoscopic instrument was more accurate in discriminating the forces than finger. The dominant hand attempted to match the forces accurately, whereas non-dominant hand (NH) overestimated the forces. Further, the NH of experts was found to be most accurate. Furthermore, excessive forces were applied at lower force levels and at very high force levels. Due to misperception of force, novices and residents applied excessive forces. However, experts had good control over force with both dominant and NHs. These findings suggest that force-based training curricula should not only have proprioception tasks, but should also include bimanual force-skills training exercises in order to improve force perception ability and hand skills of novices and residents. The results can be used as a performance metric in both box and virtual reality based force-skills training.

Force JND for Right Index Finger Using Contra Lateral Force Matching Paradigm

Abstract: The paper aims at deriving the Just Noticeable Difference (JND) for force magnitude recognition between left and right index finger of human hand The experiment involves establishment of an internal reference stimulus, using the left index fingers of the hand, by the subject, which is perceived and matched under contra-lateral force matching paradigm A combination of virtual environment and a force sensor was used to derive the just noticeable difference for index-finger force application Six voluntary healthy young adult subjects in the age group of 22–30 years were instructed to produce reference forces by left index finger and to reproduce the same amount of force by the right index finger, when the subjects were confident enough of matching same amount of force, the force values of the both the left and right index finger were recorded simultaneously for 5 s at 10 Hz Five different trials were conducted for different force levels ranging from 2 to 5 N The percentage real JND and absolute JND were derived for all the subjects It was found that the Force-JND obtained was approximately 10 % across all subjects Results also show that subjects tend to underestimate force at high force levels and overestimate at low force levels The results obtained can be used as basic building block for the calibration of virtual reality based minimally invasive surgery related tasks and force based virtual user interfaces ranging from touch pad to assistive tools

Comparison of Force Matching Performance in Conventional and Laparoscopic Force-Based Task

Abstract: Laparoscopic instruments have limited haptics feedback. Hence, novices tend to exert excessive force which leads to tissue trauma. In laparoscopic surgery, no external information is available on the magnitude of excessive force. Therefore, novices should be trained to accurately perceive their own force output. This study analyzed the force perception of 18 novices in the absence of external information, by comparing the isometric force matching performance of index finger (i.e. used in conventional procedures) in extended arm posture with that of laparoscopic instrument in a force-based probing task. The study also examined the effect of handedness on force perception. A contra-lateral force matching paradigm was employed to analyze the matching performance of the novice subjects. Interestingly, matching error was found to be lower for laparoscopic instrument. An effect of handedness was visible for laparoscopic instrument only. The dominant hand overestimated the forces of non-dominant hand. The result...

Modeling of Human Hand Force Based Tasks Using Fitts's Law

Abstract: Conventional Fitts’s model for human movement task finds a common application in modern day interactive computer systems and ergonomics design. According to Fitts’s law the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. This paper describes experimental process for prediction of minimum movement time, in a force-variation based human performance task involving right index finger. In this study we have made an attempt to extend the applicability of the conventional Fitts’s model for a force based virtual movement task, without taking position into account and evaluate human performance metrics for such tasks. An experiment was conducted in which 6 healthy young adult subject’s in the age group of 22–30 years performed force based movement tasks. During each trial, subjects were asked to reach an initial force bar of given thickness W Newtons, corresponding to allowable tolerance. Once the subject’s had reached initial level, they were instructed to reach out the target force bar of same thickness W as quickly as possible and bring it back to the initial force level bar, thereby completing 1 iteration. Time required for 10 such iteration was noted for each subject. The results from the experiment show that the relationship between movement time and index of difficulty for force tasks are well described by Fitts’s law in visual guided, force-based virtual movement task.

What is a device bend gesture really good for

Abstract: Device deformation allows new types of gestures to be used in interaction. We identify that the gesture/use-case pairings proposed by interaction designers are often driven by factors relating improved tangibility, spatial directionality and strong metaphorical bonds. With this starting point, we argue that some of the designs may not make use of the full potential of deformation gestures as continuous, bipolar input techniques. In two user studies, we revisited the basics of deformation input by taking a new systematic look at the question of matching gestures with use cases. We observed comparable levels of UX when using bend input in different continuous bipolar interactions, irrespective of the choice of tangibility, directionality and metaphor. We concluded that device bend gestures use their full potential when used to control continuous bipolar parameters, and when quick reactions are needed. From our studies, we also identify relative strengths of absolute and relative mappings, and report a Fitts' law study for device bending input.

Development of a Laparoscopic Box Trainer Based on Open Source Hardware and Artificial Intelligence for Objective Assessment of Surgical Psychomotor Skills

Abstract: Background. A trainer for online laparoscopic surgical skills assessment based on the performance of experts and nonexperts is presented. The system uses computer vision, augmented reality, and art...

Haptic Feedback in Needle Insertion Modeling and Simulation

Abstract: Needle insertion is the most basic skill in medical care, and training has to be imparted not only for physicians but also for nurses and paramedics In most needle insertion procedures, haptic feedback from the needle is the main stimulus in which novices need training For better patient safety, the classical methods of training the haptic skills have to be replaced with simulators based on new robotic and graphics technologies This paper reviews the current advances in needle insertion modeling, classified into three sections: needle insertion models, tissue deformation models, and needle–tissue interaction models Although understated in the literature, the classical and dynamic friction models, which are critical for needle insertion modeling, are also discussed The experimental setup or the needle simulators that have been developed to validate the models are described The need of psychophysics for needle simulators and psychophysical parameter analysis of human perception in needle insertion are discussed, which are completely ignored in the literature