Ergonomic design and evaluation of gemstone polishing workstation

Objectives. Gemstone polishers suffer from musculoskeletal problems due to constrained working postures, substantially influenced by the poor design of conventional gemstone polishing workstations. The present study investigated the effects of three workstation adjustment parameters (illumination at workstation, polishing height, tool post position) on postural angle, muscle activity and perceived postural discomfort in order to develop recommendations for new gemstone polishing workstations. Methods. Twelve professional gemstone polishers performed the polishing task on a prototype test-rig in 27 different test conditions. Taguchi's L27 orthogonal array was employed to estimate the optimum setting for gemstone polishing workstation design. Results. Study variables had a significant influence on postural angles. Polishing height substantially influenced muscle activity and perceived discomfort in the shoulder and lower back region. Tool post position was found to be the determinant factor for forearm muscle activity and perceived discomfort in the wrist/forearm region. Based on the findings, illumination of 1500 lux, polishing at 15 cm above the elbow height and a 20° tool position was recommended. Conclusions. Our findings present an alternative approach to using Taguchi's design of experiment for workstation improvement, which has received very little attention in ergonomics studies. A confirmation test was conducted to validate the study recommendations.

Robust Hand Motion Tracking through Data Fusion of 5DT Data Glove and Nimble VR Kinect Camera Measurements

Vision based interfaces for human computer interaction have gained increasing attention over the past decade. This study presents a data fusion approach of the Nimble VR vision based system, using the Kinect camera, with the contact based 5DT Data Glove. Data fusion was achieved through a Kalman filter. The Nimble VR and filter output were compared using measurements performed on (1) a wooden hand model placed in various static postures and orientations; and (2) three differently sized human hands during active finger flexions. Precision and accuracy of joint angle estimates as a function of hand posture and orientation were determined. Moreover, in light of possible self-occlusions of the fingers in the Kinect camera images, data completeness was assessed. Results showed that the integration of the Data Glove through the Kalman filter provided for the proximal interphalangeal (PIP) joints of the fingers a substantial improvement of 79% in precision, from 2.2 deg to 0.9 deg. Moreover, a moderate improvement of 31% in accuracy (being the mean angular deviation from the true joint angle) was established, from 24 deg to 17 deg. The metacarpophalangeal (MCP) joint was relatively unaffected by the Kalman filter. Moreover, the Data Glove increased data completeness, thus providing a substantial advantage over the sole use of the Nimble VR system.

Evaluation of four cursor control devices during a target acquisition task for laparoscopic tool control

Current laparoscopic surgery instruments create awkward postures which produce fatigue and pressure points in surgeons. In order to alleviate some of this discomfort a new laparoscopic tool had been developed with the inclusion of an articulating end-effector manipulated by a trackball. The current study was developed to access the performance of four input devices which could replace the manual trackball in a powered laparoscopic tool. A simple Fitts' law task was conducted and the devices' performance was evaluated with both subjective and objective measures. This article makes three main contributions to the scientific community. First, it provides a comparison of four control devices (TouchPad, Mouse Button Module, MiniJoystick Module and MicroJoystick) for use in a powered laparoscopic tool. Second, it provides an understanding of how the non-traditional measure of target re-entry can be utilized to compare control devices and how this relates to the more traditional measures of throughput and error rate. Finally, it contributes to the understanding of how a user's familiarity with a control device could affect the subjective and objective performance of the device. The main results indicate that the TouchPad and MicroJoystick are the best candidate-devices for use in a powered laparoscopic tool. The article also provides support for utilizing the new measure target re-entry when comparing control performance. Although studied in the application of laparoscopic surgery, the results can be generalized for the design of any hand-held device in which the speed and accuracy of the control device is critical.

Effect of handle design and target location on insertion and aim with a laparoscopic surgical tool

Two laparoscopic tools, a scissor-type grasper and an ergonomically designed grasper, were compared in terms of operation efficiency and physical workload while inserting into a simulated abdomen and aiming five cross-shaped targets. Thirty right-handed novice participants performed the tasks with five tool-grasping hand postures at two computer monitor angles that simulated reaching an organ during laparoscopic surgery. When comparing the two free style hand postures used, there was a significant improvement in operation efficiency. This demonstrated that the participants quickly became familiar with the Intuitool by finding new hand postures that will significantly help them reach the target faster and more accurately. The 45( composite function) monitor angle showed the worst accuracy and deviation, the 0( composite function) monitor angle showed the best accuracy and smallest deviation with the upper target. Thus it is recommended that the camera trocar be placed directly above the organ of interest, and the part of the organ to be reached should be displayed slightly above the center of the feedback monitor. For physical workload, the method of gripping the tools was the most important factor. The scissors-type tool caused the largest wrist flexion, in contrast both free styles hand postures with the Intuitool showed the least wrist flexion.