Changes between Version 5 and Version 6 of Hand/280/KinematicsJointRangesConversionFactors


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Timestamp:
Jul 18, 2013, 4:13:37 PM (6 years ago)
Author:
dc
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  • Hand/280/KinematicsJointRangesConversionFactors

    v5 v6  
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    234 This section describes all mechanical reductions in the 262 and 280 hands as well as the ratios that go from finger and spread encoder positions to joint positions in units of radians.  To find the finger or spread mechanical reduction relative to the motor  use the constants in the table below.  Table 10 applies to the hands before breakaway occurs.  Each finger has 3 joints starting with the knuckle joint that swings the spread, the last one moves the outer link, and the one in between moves an amount proportional to the outer link until breakaway occurs.  To go from motor encoder position to actual finger position for joint 2 multiply the encoder position by the corresponding joint Radians to ticks ratio.  Joint 3 of the finger moves one third this amount.  This transformation works before breakaway of the !TorqueSwitch™ has occurred.
     234This section describes all mechanical reductions in the 262, 280 and 282 hands as well as the ratios that go from finger and spread encoder positions to joint positions in units of radians.  To find the finger or spread mechanical reduction relative to the motor  use the constants in the table below.  Table 10 applies to the hands before breakaway occurs.  Each finger has 3 joints starting with the knuckle joint that swings the spread, the last one moves the outer link, and the one in between moves an amount proportional to the outer link until breakaway occurs.  To go from motor encoder position to actual finger position for joint 2 multiply the encoder position by the corresponding joint Radians to ticks ratio.  Joint 3 of the finger moves one third this amount.  This transformation works before breakaway of the !TorqueSwitch™ has occurred.
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    248 The optical encoders for each of the 280 hand motors have 4096 count encoders and 262 hand motors uses a 90 line, or 360 count, encoder.  Inner link encoders are the same ones used on the motor for position feedback.
     248The optical encoders for each of the 280 and 282 hand motors have 4096 count encoders and 262 hand motors uses a 90 line, or 360 count, encoder.  Inner link encoders are the same ones used on the motor for position feedback.
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    250250The forward kinematics from section 9.5, that are used to calculate end-tip positions, depend on the configuration of joint positions for each finger (joint 2 and joint 3) and the spread.  Calculate positions in radians for each joint including spread, finger joint 2, and finger joint 3.  These will be the joint positions before breakaway.
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    252 Joint 3 position can be represented more precisely if it is calculated relative to the plane of the palm plate that is accurate before and after breakaway.  This position for joint 3 depends only on the model number (262 or 280) of the hand where [[Image(htdocs:phi.png)]],,3,, is a joint 3 offset from joint 2 equal to approximately 42°.
     252Joint 3 position can be represented more precisely if it is calculated relative to the plane of the palm plate that is accurate before and after breakaway.  This position for joint 3 depends only on the model number (262, 280 or 282) of the hand where [[Image(htdocs:phi.png)]],,3,, is a joint 3 offset from joint 2 equal to approximately 42°.
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    262 Note that joint 1 in the knuckle drives the outer link first through a 93.75 reduction and then a 4:1 reduction.  The motor position directly determines the outer link angle with the palm plate of the hand as shown in Equation 4.  During breakaway joint 2 position needs to be detected in software by using breakaway  acceleration threshold for the 262 hand and then this link remains motionless as described in section 9.3.  The breakaway position may be used for finding where breakaway occurred.  Joint 3 position still only depends on just absolute motor position.  On 280 hands, the inner-link joint position sensors may be used together with the outer link position to determine the finger positions at all times.
     262Note that joint 1 in the knuckle drives the outer link first through a 93.75 reduction and then a 4:1 reduction.  The motor position directly determines the outer link angle with the palm plate of the hand as shown in Equation 4.  During breakaway joint 2 position needs to be detected in software by using breakaway  acceleration threshold for the 262 hand and then this link remains motionless as described in section 9.3.  The breakaway position may be used for finding where breakaway occurred.  Joint 3 position still only depends on just absolute motor position.  On 280 and 282 hands, the inner-link joint position sensors may be used together with the outer link position to determine the finger positions at all times.
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    264264=== Joint Motion Limits ===