ME EN 4000 Senior DesignDate: 19 October 2005To: Dr. ProvancherCC: Andy Dohanos, Rebacca DaPraFrom: Team Robot HandJared WoodCameron SullivanAaron LassigSubject: Memo 3: CFPAttachments: 1IntroductionThis memo presents information regarding- Schedule and status- Benchmarking continued- Work update- Design concepts and critical function prototype (CFP)Schedule and StatusA CFP design has been selected, which means team Robot Hand is on track. The schedule to follow is- 23 October Week—detail CFP design- 01 November Week—begin construction- 08 November Week—complete CFPBenchmarking ContinuedTeam Robot Hand continues to benchmark. Figure 1 is the Stanford-JPL Hand and Figure 2 is the Omni and Herzinger hands. The Stanford-JPL Hand has the capability to hyperextend. The Omni Hand has exterior tendons and the Herzinger Hand has interior tendons.Work UpdateWork done since the previous memo is- Concept generation- Concept combination- Decision matricesConcepts regarding the 3 research areas (actuator design, power transmission, mechanism design) have been developed. Within the actuator design are- Figure 3: full-force series shape memory alloy (SMA) contraction magnification- Figure 4: ½ force series SMA equal-contraction magnification- Figure 5: almost full-force series SMA contraction magnificationFigure 3 shows possibility of magnifying the SMA contraction within a more compact region. SMA wires only contract approximately 4% of their length. Additionally, with many 1independent actuators in series, it’s possible to achieve various degrees of tendon contraction, leading to various finger positions. This design provides better controllability because SMA wires contract nonlinearly and have different dynamics on contraction than they have on expansion. Figure 4 shows possibility to achieve a similar system, except with equal SMA contraction, providing even simpler control. The disadvantage of this concept is that only ½ of the SMA force is transmitted to the tendons. Figure 5 shows another progressed concept of the series SMA contraction magnification. The advantage of this concept is that it achieves superior compactness when compared with Figures 3 and 4. Within power transmission is- Figure 6: reverse bias possibilityFigure 6 shows that reverse bias is possible. The advantage of reverse bias is that SMA wires do much better with it, resulting in greater percent contraction per unit length. The disadvantage is that the tendons would protrude upon flexion and the dynamics would be more complicated. Power transmission is also implicitly dealt with in the mechanism design concepts, which are- Figure 7: wire-frame, interior tendons- Figure 8: solid, exterior tendons- Figure 9: Solid, exterior tendons, anthropomorphic tendon system, only 3 actuators total- Figure 10: wire-frame, interior tendons, adjustable axis- Figure 11: solid, interior tendonsFigure 7 presents a concept which allows small joint radii by using a wire-frame with interior tendons. Figure 8 shows possibility to achieve very small joint radii by having exterior tendons. Figure 9 show possibility of an anthropomorphic tendon system. The main advantage of this concept is that only 3 actuators are required, whereas the other designs require 2 actuators for each joint. Figure 10 is a developed wire-frame which has an adjustable axis to allow reverse bias. Figure 11 portrays a concept which shows possibility of a solid finger with interior tendons.Decision matrices were used to determine which aspects of each concept are desirable and to determine which concepts will be implemented into the CFP.Design Concepts and CFPThe CFP will be versatile so that multiple concepts could be used and alternated to determine themost appropriate design. Accordingly, the CFP will be a wire-frame with an adjustable axis and possibilities for interior and exterior tendons.ConclusionTeam Robot Hand is on track. The next step is to detail the CFP design and begin construction. Benchmarking continues. Work done since the previous memo is concept generation, concept combination, and decision matrices to determine the best concepts. From the concepts, the CFP was chosen to allow various concepts to be used and tested. The concepts carried to the CFP are wire-frame, adjustable axis, and interior and exterior tendon routes.Attachment2Figure 1: Stanford-JPL Hand; http://vesuvius.jsc.nasa.gov/er_er/html/dart/hands.htmlFigure 2: Omni and Herzinger hands; http://www.robotics.utexas.edu/rrg/learn_more/high_ed/grasp/designs/omni.htmlhttp://www.robotics.utexas.edu/rrg/learn_more/high_ed/grasp/designs/hirzinger.html3Figure 3: Full-force series SMA contraction magnificationFigure 4: ½ force series SMA equal-contraction magnificationFigure 5: Almost full-force series SMA contraction magnification4Figure 6: Reverse bias possibilityFigure 7: Wire-frame, interior tendons5Figure 8: Solid, exterior tendonsFigure 9: Solid, exterior tendons, anthropomorphic tendon system, only 3 actuators totalFigure 10: Wire-frame, interior tendons, adjustable axis6Figure 11: Solid, interior