Changes between Version 16 and Version 17 of Hand/280/KinematicsJointRangesConversionFactors

Timestamp:

Jan 7, 2016, 10:57:32 PM (8 years ago)

Author:

cv

Comment:

--

Hand/280/KinematicsJointRangesConversionFactors

@@ -3 +3 @@
 == Finger Drivetrain and TorqueSwitch™ ==
 
-It is easiest to understand Barrett's patented TorqueSwitch™ mechanism by first understanding the operation of the BarrettHand finger assembly.  The image below shows a single finger, including all critical drive elements, with the motor windings and rest of the hand hidden.
+It is easiest to understand Barrett's patented TorqueSwitch™ mechanism by first understanding the operation of the BarrettHand finger assembly.  Figure 1 shows a single finger, including all critical drive elements, with the motor windings and rest of the hand hidden.
 
 {{{
@@ -9 +9 @@
 [[Image(htdocs:bhand/282/OverallFinger.png)]]
 
-'''Single BarrettHand Finger Assembly'''
-}}}
-
-
-This second image is a close-up of the drive elements in the finger.  During normal operation, the 16-tooth motor pinion (gray) drives both the 30-tooth distal (yellow) and 40-tooth proximal (blue) gears, which transmit power through their respective worms (red and green) and into two 50-tooth worm gears (orange and purple).  The proximal worm gear (purple) is tied directly to the proximal link with six screws, whereas the distal gear (orange) connects to the distal link via mechanical cables.  The net result is a motion ratio of 93.75:1 for the motor shaft to proximal joint position and a 125:1 reduction for the motor shaft to distal joint position.  Also, note the two magnets (light blue) and their associated Hall-array sensors (black) at the ends of the motor shaft and worm shaft.  These two encoders allow the Puck to determine the position of both joints in the finger (the proximal link via the worm sensor and the distal link via the motor sensor).
+'''Figure 1 - Single BarrettHand Finger Assembly'''
+}}}
+
+
+Figure 2 is a close-up of the drive elements in the finger.  During normal operation, the 16-tooth motor pinion (gray) drives both the 30-tooth distal (yellow) and 40-tooth proximal (blue) gears, which transmit power through their respective worms (red and green) and into two 50-tooth worm gears (orange and purple).  The proximal worm gear (purple) is tied directly to the proximal link with six screws, whereas the distal gear (orange) connects to the distal link via mechanical cables.  The net result is a motion ratio of 93.75:1 for the motor shaft to proximal joint position and a 125:1 reduction for the motor shaft to distal joint position.  Also, note the two magnets (light blue) and their associated Hall-array sensors (black) at the ends of the motor shaft and worm shaft.  These two encoders allow the Puck to determine the position of both joints in the finger (the proximal link via the worm sensor and the distal link via the motor sensor).
 
 {{{
@@ -19 +19 @@
 [[Image(htdocs:bhand/282/FingerDriveElements.png)]]
 
-'''BarrettHand Finger Drive Elements'''
+'''Figure 2 - BarrettHand Finger Drive Elements'''
 }}}
 
 The connection between the proximal worm (green), the belleville washers (pink) and the proximal gear (blue) is the critical part of this assembly that makes the TorqueSwitch™ work.  The proximal gear is internally threaded, and rides on right-handed threads cut into the worm shaft, while the belleville washers are compressed between the side of the gear and a shoulder on the shaft.  The compressed bellevilles create Coulomb friction in the assembly that holds the gear stationary relative to the worm.
 
-When the proximal link contacts a surface, the resultant torque in the worm causes the gear to "break away" from the Coulomb friction and wind off the washers along the shaft.  The sequence of images below shows this process.
+When the proximal link contacts a surface, the resultant torque in the worm causes the gear to "break away" from the Coulomb friction and wind off the washers along the shaft.  Figures 3 through 5 show this process.
 
 {{{
@@ -30 +30 @@
 [[Image(htdocs:bhand/282/PreBreakaway.png)]]
 
-'''The worm and proximal gear rotate together at first, linked across the belleville washers via Coulomb friction.'''
+'''Figure 3 - The worm and proximal gear rotate together at first, linked across the belleville washers via Coulomb friction.'''
 }}}
 
@@ -38 +38 @@
 [[Image(htdocs:bhand/282/Breakaway.png)]]
 
-'''When the proximal link encounters adequate resistance torque, the friction breaks away and the proximal gear winds off the belleville washers.  From this point forward, the proximal link remains locked in place.'''
+'''Figure 4 - When the proximal link encounters adequate resistance torque, the friction breaks away and the proximal gear winds off the belleville washers.  From this point forward, the proximal link remains locked in place.'''
 }}}
 
@@ -46 +46 @@
 [[Image(htdocs:bhand/282/PostBreakaway.png)]]
 
+'''Figure 5'''
+
 '''The proximal gear then winds up the worm shaft, directing motor torque to drive the distal link.'''
 
@@ -56 +58 @@
 The TorqueSwitch™ is reset by opening the finger.  First, the distal link will open as the proximal gear winds along the shaft, then drive the proximal gear against the belleville washers, re-engaging the clutch and causing the proximal link to open with the distal link.  When the proximal link encounters a resistive force, such as its joint stop, the proximal gear will compress the bellevilles, preloading the system to a programmable level (Puck parameter "OT").
 
-The following graph can be used to set OT for your application:
+Figure 6 can be used to set OT for your application:
 
 {{{
@@ -62 +64 @@
 [[Image(htdocs:bhand/280/figure31.png)]]
 
-'''Figure 31 - Breakaway Force Curve'''
-}}}
-
-To control how much force is applied to an object being grasped without sensor feedback such as finger-tip torque sensors (strain gauges) or tactile sensors, the MT property must be used. Please see this graph to see how MT and finger torque are related:
-
-http://web.barrett.com/support/BarrettHand_Documentation/MotorTorque280.png
+'''Figure 6 - Breakaway Force Curve'''
+}}}
+
+To control how much force is applied to an object being grasped without sensor feedback such as finger-tip torque sensors (strain gauges) or tactile sensors, the MT property must be used. Please see Figure 7 to see how MT and finger torque are related:
+
+{{{
+#!div class="center" align="center"
+[[Image(htdocs:bhand/280/MotorTorque280.png)]]
+
+'''Figure 7 - Motor Torque vs. Property "T"'''
+}}}