Whitney says the device has greater torque per weight (torque density) than highly geared servos or brushless motors coupled with harmonic drives. And more significant: To build an autonomous robot, you'd need a set of motors and a control system capable of replacing the human puppeteer who's manually driving the fluid actuators [below]. John P. Whitney: The original motivation was the same as for the MIT WAM arm and other impedance-based systems designed for human interaction: Using a lightweight high-performance transmission allows placing the drive motors in the body, instead of suffering the cascading inertia if they were placed at each joint. We are learning that many of the "analog" qualities of this system will pay dividends for autonomous "digital" operation; for example, the natural haptic properties of the system can be of equal service to an autonomous control system as they are to a human operator.
Roboticists have long been trying to build robot arms that are light, nimble, and safe to operate near people. Some designs rely on compliant actuators, artificial muscles, or sensors and software to keep the arms from smashing into things that they're not supposed to. The challenge, however, is that most robot arms are stuffed full of electric motors and gears, and these are relatively big and heavy, adding to the size and weight of the arms. Now engineers at Disney Research have come up with an ingenious way of making robot arms that are low mass but high speed. Instead of conventional motors, their arm uses what's called a fluid transmission.
In the opening mode, fluid inertia and dissipative effects in the clearance between land and port, cause a second order buildup of fluid flow. Though the fluid flow velocity and its time derivative are 0 initially, the velocity of the elevator and the driving piston are not. This results in a pressure buildup in the cylinder governed by the elasticity coefficient of the oil which causes a rapid increase of fluid flow through the land/port opening. The pressure also causes the elevator velocity to decrease rapidly resulting in the transient in Figure 1(a). The initial transient from moving into the closed mode is replaced by the transient moving into the opening mode.
Due to the needs originated from intense market transformations, i.e. increasing competitiveness, technological advances as well as economic globalization, more companies have been applying Concurrent Engineering techniques. In this context, the time to market is as important as the product quality, some researches show that 80% of a market for a new product is shared with the first two companies which launch the product (Brazier and Leonard 1990). In order to cope with this environment, multidisciplinary teams grouping, for example, engineers, designers and market analysts are being integrated to search for ways of creating quickly and more efficiently new products through collaborative Concurrent Engineering efforts. There are many definitions for concurrent engineering, one of them is quoted as follows: Concurrent Engineering is as a systematic approach to the integrated, concurrent design of products and their related processes, including manufacture and support. This approach is intended to cause the developers, from the outset, to consider all elements of the product life cycle from conception through disposal, including quality, cost, schedule, and user requirements (Klement 1993).