Compact dexterous robotic hand

Details Compact dexterous robotic hand Compact dexterous robotic hand

1999-01-25

2001-06-12

Kramer, Dean J. (Department: 3652)

Handling: hand and hoist-line implements

Grapple

Pivoted jaws

C294S907000, C901S029000, C901S036000, C901S046000

Reexamination Certificate

active

06244644

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a compact, rugged, dexterous robotic hand that closely resembles the function of a human hand. In particular, the robotic hand includes highly reliable yet simple components which enable the desired movement and function of a plurality of flexible fingers attached to a palm housing, a thumb, and a wrist member. Force is mechanically transmitted from drive components in a forearm portion through the wrist section to operate the plurality of fingers and thumb.
BACKGROUND OF THE INVENTION
The dexterity of the human hand enables it to execute complex and agile movements. Simulated movement of the human hand thus desirably achieves movement in directions having degrees of freedom similar to those in the human hand. Robotic simulation of movement in the human hand is practically limited by the size and weight of the components needed to simulate movement. The size of a robotic hand has conventionally suffered at the expense of obtaining the desired motion, and the desired dexterity of fingers and a thumb are achieved in a complex mechanism which still has limited capabilities. The action of these components does not closely approximate the desired movement of a human hand, and thus control of the robotic hand by a “smart glove” is less accurate.
Robotic devices simulating movement of the human hand frequently tend to sacrifice one or more desired simulated functions for other desired simulated functions. Many robotic hand devices focus on simulating the overall appearance and movement of the human hand while neglecting other equally important features such as the size, weight, mobility and control of the robotic device. Conventional robotic devices are therefore relatively complex, large, cumbersome and difficult to use. The complexity of conventional robotic devices also has resulted in robotic hands which are expensive to manufacture, and are also expensive to maintain.
U.S. Pat. No. 4,986,723 to Maeda and U.S. Pat. No. 5,447,403 to Engler, Jr. each describe a conventional robotic hand. Maeda describes a robot arm that comprises four flexible fingers and a thumb wherein each flexible finger and thumb includes three joints. Pulleys are provided on each joint so that each joint can be bent. The third joint has approximately one-half the bending motion of the second joint. The robot arm described by Maeda offers 18 degrees of freedom that resembles movement of a human arm. As a result, 18 actuators or motors are required to operate this cable wire and pulley system of Maeda. Similarly, Engler, Jr. describes a dexterous programmable robot and control system that includes a hand with four fingers and a thumb. Each finger and thumb have four degrees of freedom which are driven by a cable and pulley system not unlike Maeda. Both Maeda and Engler, Jr. rely upon a complex mechanical drive train to affect bending and rotational movement in the joints provided in the fingers and thumb. As a result, the robotic hands described by Maeda and Engler, Jr. are unreasonably large, heavy and cumbersome, making it difficult to grasp and control delicate or light objects with reasonable precision.
Other conventional robotic devices attempting to simulate movement of the human hand are described by U.S. Pat. No. 4,046,262 to Vykukal et al.; U.S. Pat. No. 4,350,381 to Hellmann; U.S. Pat. No. 4,921,293 to Ruoff et al.; U.S. Pat. No. 5,378,033 to Guo et al.; U.S. Pat. No. 5,347,490 to Mimura et al.; U.S. Pat. No. 5,476,357 to Arai; U.S. Pat. No. 5,570,920 to Crisman et al.; and U.S. Pat. No. 5,588,688 to Jacobson et al. These conventional devices are quite complex and thus expensive, and also are limited by many of the disadvantages described above.
Accordingly, there is a specific need for a dexterous robotic hand that closely resembles the anatomical movement of the human hand yet is lightweight, mobile and capable of grasping both heavy and light object s with precision.
SUMMARY OF THE INVENTION
The dexterous robotic hand generally comprises of a palm housing and a plurality of flexible fingers and a thumb that are each moveably secured to the palm housing. In a preferred embodiment, the dexterous robotic hand includes a forearm section which houses the drive motors and electronics which enable the controlled movement of the fingers and the thumb. The robotic hand includes a two degree of freedom wrist section and a twelve degree of freedom hand that are each discussed in further detail below. The hand includes two dexterous fingers and a thumb each with three degrees of freedom, two grasping fingers each with one degree of freedom, and a hinged palm with one degree of freedom.
The forearm section houses the drive motors, hereinafter also referred to as actuators, as well as the corresponding electronics and wiring, thereby conserving space in the palm housing. The wrist section includes a wrist cuff having a central opening for transmitting power from the drive motor to the fingers, as explained subsequently. A first and a second shockloader may be interconnected between opposing sides of the wrist section and the forearm section for mitigating stress exerted on the robotic hand.
Wrist actuators positioned in the forearm section are operably connected to the palm housing and enable the simultaneous pivotal movement of the robotic hand in directions having at least two degrees of freedom, i.e., the wrist cuff may pivot vertically (pitch) with respect to the forearm section and the palm housing may pivot laterally (yaw) with respect to the wrist section. A wrist sensor may be attached to each of the pair of wrist actuators for sensing the relative position of the wrist section with respect to the forearm section. A plurality of strain gauges may be positioned between the palm housing and the wrist actuators for sensing force on the wrist section.
The robotic hand preferably includes one or more dexterous fingers primarily used for manipulation of an object and one or more grasping fingers primarily used to maintain a stable grasp on the object. In a preferred embodiment, the two dexterous fingers functionally resemble the index and middle fingers (first and second) on the human hand and each allow for three degrees of freedom. The two grasping fingers are each one degree of freedom fingers that functionally resemble the ring and pinkie fingers (third and fourth) on the human hand. The thumb has three degrees of freedom and is skewed with respect to the palm housing to oppose the dexterous fingers. Each grasping finger is positioned opposite the thumb relative to the dexterous fingers. Each finger includes a plurality of hingedly connected segments that resemble the segments of a respective finger on the human hand. A segment sensor may be attached to each of the plurality of hingedly connected segments on a respective finger to sense the relative position of that finger segment as it bends relative to the palm housing.
A shock mount may be positioned between the palm housing and a respective finger for mitigating stress transferred to the finger when jarred towards the palm housing either while the finger is in an opened (extended or straight) position or while the finger is in a closed (bent or grasping) position. The shock mount increases the tolerance of each respective finger to withstand abnormal and/or excessive loads placed thereon, thus improving the overall durability of the robotic hand.
A groove may be provided in the proximal segment of each finger, which is a finger segment connected to the palm housing. The groove defines a first curvilinear cam surface and a second curvilinear cam surface. The second curvilinear cam surface is arced in a direction opposite the first curvilinear cam surface, such that the instantaneous center of curvature of the second cam surface is opposite the groove with respect to the instantaneous center of curvature of the first cam surface.
A plurality of lead screw assemblies are carried by the palm housing. Each lead screw assembly includes a short flexible cable having a coupling end connected to the proximal fin

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