|
|
 |
|
|
Research |
|
|
| |
|
|
|
Mechanical Design
The hand
utilizes a Watt 6-Bar Linkage for coupling actuator motion for both
the distal and proximal joints of a single finger. This allows one
actuator to emulate the joint ranges of the proximal and distal
joints of the human phalange.
Sensors
The initial hand design
will be limited to five force sensitive resistors (FSRs). Each
finger's inside distal pad will contain an FSR that varies its
resistance based on the force exerted on its surface. Additionally,
one FSR will reside in the palm.
These
FSRs provide the hand with feedback from its environment. One reason
for this is to simplify the control of the hand. A priori
knowledge of the obstacle to be grasped will allow us to set a force
threshold and determine a grasping strategy to successfully obtain
the object. A behavior-based implementation will demonstrate this
strategy.
The backside of the palm will
contain the circuitry for the FSRs. A 20-pin DIN connector will
interface this circuit to the PC card's 16-bits of digital I/O. 3
bits of digital output will select an octal latch or an 8-bit A/D
converter for driving the 8-bits of digital input to the PC card's
I/O. An analog input will also be selected on the 8-channel, 8-bit
A/D converter. Future expansion will be facilitated by the addition
of octal latches for simple tactile information. 3 channels of
analog input will also be available.
Behaviors
Reflexive
GraspingA grasping behavior is implemented based on the first
grasping patterns of the neonates which are driven by sensory inputs
to the palmar surface. Put simply, when a force is perceived at the
palm's force sensitive resistor that exceeds some threshold, the
fingers will close in an attempt to grasp the object.
Force-Based GraspingThis is a
high level behavior used to grasp objects based on a priori
knowledge. A grasping force and a simple boolean command
(OPEN,CLOSE) are given to this behavior. If the fingers close at the
given grasping force without registering any forces, this behavior
issues an error message that is relayed to higher-level agents of
the system. |
|
