A user interface for a seven degree of freedom surgical robot

[摘要] ENGLISH ABSTRACT: This thesis describes the process of developing a user interface for a sevendegree of freedom (DOF), minimally invasive surgical robot. For the first two mainstages of the overall project, completed by previous students, a primary slavemanipulator (PSM) and a secondary slave manipulator (SSM) were developed.The stage in this thesis concentrates on creating a joystick that can control thecombined movement of the PSM and SSM.Background information on the field of robotic surgery, with specific reference tocurrent systems' user interfaces, is given and the technical aspects of the PSMand SSM are determined. This is followed by the motivation and main objectivesof the thesis. Objectives were divided into the main categories of mechanicaldesign, electronic design, control system design and testing.The mechanical design of the joystick progresses through a conceptdevelopment stage, before a final seven DOF articulated arm design is presentedand evaluated based on engineering specifications. Aluminium is used as theconstruction material; electromagnetic brakes are specified for each joint, leadingto the final assembly, which is a constructed joystick fulfilling all requirements.The electronic design implements magnetic rotary encoders for the joystick'sposition and orientation tracking as well as designs of the necessary power andcontrol circuitry to enable correct joystick functioning. The interfacing of the PSMand SSM had to enable successful communication capabilities between themaster and the slave. Several necessary adjustments were therefore made to theslave system, after which the joystick and robot were electronically interfaced toprovide a direct serial communication line.For control system design, the joystick and robot were modelled according to theDenavit-Hartenberg principle, which allows direct relation between the positionand orientation of the respective end effectors on the joystick and robot sides.Forward kinematic equations were then applied to the joystick; the desiredposition and orientation of the robot end effector were determined, and inversekinematic equations were applied to these data to establish the robot's jointvariables. This stage ended with the development of two operational modes: onewhere only the SSM motors are controlled in order for the slave to follow themaster's movements, and the other where the PSM's motors are controlledseparately. The simultaneous control of all robot motors could not bedemonstrated due to fundamental mechanical flaws in the PSM and SSMdesigns.Finally, testing was undertaken to demonstrate movement control of the robot bythe joystick. The intuitiveness of the product was also tested successfully. Thestudy ends with the presentation of the conclusions, the main conclusions beingthe successful development and testing of a joystick that controls the movementof a surgical robot, as well as the achievement of all main thesis objectives.

[发布机构] Stellenbosch University