Engineering topics
Publications and source records attributed to Tsai, Lung-Wen.
Six-degree-of-freedom parallel minimanipulator stiffer and simpler than earlier six-degree-of-freedom manipulators. Includes only three inextensible limbs with universal joints at ends. Limbs have equal lengths and act in parallel as they share load on manipulated platform. Designed to provide high resolution and high stiffness for fine control of position and force in hybrid serial/parallel-manipulator system.
A Six-Degree-of-Freedom Parallel-Manipulator having three inextensible limbs for manipulating a platform is described. The three inextensible limbs are attached via universal joints to the platform at non-collinear points. Each of the inextensible limbs is also attached via universal joints to a two-degree-of-freedom parallel driver such as a five-bar linkage, a pantograph, or a bidirectional linear stepper motor. The drivers move the lower ends of the limbs parallel to a fixed base and thereby provide manipulation of the platform. The actuators are mounted on the fixed base without using any power transmission devices such as gears or belts.
A new class of six-degree-of-freedom parallel minimanipulators capable of providing high resolution and high-stiffness for fine position and force control in a hybrid serial-parallel manipulator system is presented. Positional resolution and stiffness of minimanipulators are improved using two-degree-of-freedom planar linkages as drivers. The minimanipulators are based on only three inextensible limbs, as opposed to most of the six-limbed parallel manipulators, which makes it possible to reduce its direct kinematics to solving a polynomial in a single variable and to diminish possibility of mechanical interference between limbs. The base-mounted minimanipulator actuators are characterized by high payload capacity, small actuator size, and low power dissipitation.
Flex-Gears are being developed as an alternative to brushes and slip rings to conduct electricity across a rotating joint. Flex-Gears roll in the annulus of sun and ring gears for electrical contact while maintaining their position by using a novel application of involute gears. A single Flex-Gear is predicted to transfer up to 2.8 amps, thereby allowing a six inch diameter device, holding 30 Flex-Gears, to transfer over 80 amps. Semi-rigid Flex-Gears are proposed to decrease Flex-Gear stress and insure proper gear meshing.
The University of Maryland Walking Machine team designed and constructed a robot. This robot was completed in two phases with supervision and suggestions from three professors and one graduate teaching assistant. Bob was designed during the Fall Semester 1991, then machined, assembled, and debugged in the Spring Semester 1992. The project required a total of 4,300 student hours and cost under $8,000. Mechanically, Bob was an exercise in optimization. The robot was designed to test several diverse aspects of robotic potential, including speed, agility, and stability, with simplicity and reliability holding equal importance. For speed and smooth walking motion, the footpath contained a long horizontal component; a vertical aspect was included to allow clearance of obstacles. These challenges were met with a leg design that utilized a unique multi-link mechanism which traveled a modified tear-drop footpath. The electrical requirements included motor, encoder, and voice control circuitry selection, manual controller manufacture, and creation of sensors for guidance. Further, there was also a need for selection of the computer, completion of a preliminary program, and testing of the robot.