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Background A surgeon performs various surgical actions with the help of teleoperation technology during robot assisted minimally invasive surgery. The slave manipulators reproduce every movement of the surgeon's hands, completely and faithfully. However, in some cases, unexpected collisions between surgical instruments and fragile organs might occur around the lesion, causing further injury. Method Marking critical areas near the surface of each vulnerable organ and generating virtual fixtures, based on which to constrain the slave manipulator motion to prevent any unexpected collision. Result Virtual fixtures can be easily defined using the proposed method before or even during the surgery as the surgeon wishes. The experimental results show that the virtual fixtures can protect the organs very well during surgical manipulation. Conclusion The proposed method can easily be applied to any master–slave minimally invasive surgical (MIS) robotic system to increase the safety of robot‐assisted surgery. Copyright © 2013 John Wiley & Sons, Ltd.

Purpose -A walking assistant robot can help elderly people walk around independently, which could improve the life quality of the elderly and benefit our aging society. Ensuring the elderly person's walking comfort with such a robot is very important. At present, the majority of walking assistant robot research does not focus on this field. The purpose of this paper is to examine the requirements of comfortable walking and outline the design of a motion control algorithm for a walking assistant robot, Walkmate III, based on comfort. Design/methodology/approach -During walking, the walking assistant robot should be able to capture the intent of user, guide the user and move at the same pace as the user. Usually, force or haptic interface is used to detect the user's walking intention. The motion control system then transforms the forces applied by the user into the robot's motion. By surveying the elderly people at a nursing home, the authors find that this transformation is important to the walking comfortableness and should be carefully designed. In this paper, the model of walking assisting process with such kind of walking assistant robot is derived at first. Based on this model, a new motion control algorithm is then designed. Findings -The elderly hoped that, in all topographic conditions, only small forces were needed to drive the walker during walking. Also, good maneuverability was also very important for a walker, to offer the user comfort, which meant the walking assistant robot should be able to respond to the input forces quickly and precisely. Currently widely-used motion control algorithms cannot satisfy all those requirements. In this paper, a new motion control algorithm is proposed, which can get a fast and precise response to the input forces and the input forces needed to drive the robot are kept at a preferred small level, so that the user will not feel tired during walking. Furthermore, by modifying, force feedback can be realized to improve the comfortableness of walking. Practical implications -The availability of walking assistant robot with improved walking comfortableness might encourage a wider adoption of robotics in our daily life. It could also benefit our aging society by improving the life quality of the elderly and reducing the pressure deriving from nursing labor shortages. Originality/value -This paper is of value to engineers and researchers developing walking assistant robots for the elderly people.

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