The palm was created using a modular cavity design. It was designed using ProEngineer and printed using Rapid Prototype.

The fingers were made using Polymorph. Their design specifications were a length of 120 mm and a width of 20 +/- 2 mm. Four joints are seen instead of three- the last is to mimic flexibility of the human palm when closing.

Force sensing resistors, placed on each fingertip, were used to detect a touch. The sensors decrease in resistance with an increase of applied force, so they were used in conjunction with an inverting operational amplifier circuit.

The fingers are controlled individually by stepper motors. Each motor is connected to a driver card which accepts a step pulse and direction from the microcontroller. These 5 driver cards are mounted on a circuit board that also contains the microcontroller and two 16 pin IC sockets.

Hardware

EasyDriver v3

Gnd V+

Step Dir

Motor Wires

To Microcontroller

To 12V 4AAC to DC

power supply

EasyDriver Card Connections

Brown Orange Red YellowRed Blue Green Black

Motor Wires By Color

Introduction and RequirementsThe Center for Intelligent Systems is a research group whose goal is to advance the state of the art in intelligent systems such as autonomous robots through development in the areas of skill learning, perception learning, and task learning. The CIS Anthropomorphic Hand project, sponsored by Dr. Kazuhiko Kawamura of CIS, aims to create a humanoid hand for the ISAC robot currently used in the cognitive robotics laboratory.

The project has the following specifications:

1.The hand must be an anthropomorphic right hand, necessitating four digits and a thumb, each with humanoid joints and grasping action.2.The total mass of the hand cannot exceed 1 kg.3.The hand must be durable; it must be able to survive an impact due to arm malfunction.4.The hand should possess independent finger control and should also be able to perform three distinct grasping functions: a full hand close, a two-finger (thumb and index) pinch, and a three-finger (thumb, index, and middle) grasp.5.There should be feedback from the fingers to the control unit to indicate when a touch occurs.

The main purpose of the program on the HCS12 microcontroller is to transition between electronic control and physical manifestation of this project. The code was developed in C using Freescale's CodeWarrior IDE. The microcontroller receives commands from the host computer via the serial port, then translates these commands into a sequence of pulses that instruct the driver cards on how to move the motors in the correct direction, at the correct speed, and for the correct period of time.

The computer software provides the interface between the user and the microcontroller. It provides the user with the ability to close and open the fingers and set control variables. The software is written in Visual C++ using Microsoft Visual Studio. The main software is a C++ class composed of a header file (Hand.h) and a source file (Hand.cpp). There are two provided applications which make use of the Hand class: a Console Application and a Windows Forms Application. The Windows Forms Application provides a graphical user interface.

Open_Fingers called

Is the microcontroller connected?

Attempt to connect to microcontroller

Successful?

Exit Function

Is it a valid parameter?Send Correct Data

Byte

Wait for response

Was a ‘DONE’ returned?

Update finger status variables

YES

NO

YES

NO

YES

YES

NO

NO

Open_Fingers(Open cmd)

EasyDriver v3Card A

Gnd V+

Step Dir

Motor Wires

To Motor A

EasyDriver v3Card B

Gnd V+

Step Dir

Motor Wires

To Motor B

EasyDriver v3Card D

Gnd V+

Step Dir

Motor Wires

To Motor D

EasyDriver v3Card E

Gnd V+

Step Dir

Motor Wires

To Motor E

EasyD

river v3C

ard C

Gnd

V+

Step

Dir

Motor W

ires

To

Mo

tor C

To V+ on 12 V 4 A AC to DC Power Supply

To Gnd on 12 V 4 A AC to DC Power Supply

Driver Card A V+

Driver Card B V+

Driver Card C V+

Driver Card D V+

Driver Card E V+

Driver Card A Step

Driver Card D Step

Driver Card A Gnd

Driver Card B Gnd

Driver Card C Gnd

Driver Card D Gnd

Driver Card E Gnd

Driver Card A Dir

Driver Card D Dir

Driver Card B Step Driver Card B Dir

Driver Card C Step

** Driver Card A Step

** Driver Card B Step

** Driver Card C Step

** Driver Card D Step

** Driver Card E Step

Driver Card E Step

Driver Card C Dir

** Driver Card A Dir

** Driver Card B Dir

** Driver Card C Dir

** Driver Card D Dir

** Driver Card E Dir

Driver Card E Dir

** Debug Pins are used for connecting motors when the microcontroller is being programmed and tested on the project board.

Driver Card Connection Board

Control Lines for Touch Sensor CircuitReset Switch Gnd

Microcontroller

Motor Step Thumb

Motor Step Index

Motor Step Middle

Motor Step Ring

Touch Sensor Thumb

Touch Sensor Index

Touch Sensor Middle

Touch Sensor Ring

Touch Sensor Pinky

Motor Direction Thumb

Motor Direction Index

Motor Direction Ring

Motor Direction Pinky

Microcontroller Connections

Touch Sensor Circuits

Motor Direction Middle

Motor Step Pinky

Reset Switch

The system is composed of five major components:

1.Five fingers fashioned with Polymorph and providing feedback by means of a touch sensor at each fingertip. 2.A palm printed using Rapid Prototype.3.Five bi-polar stepper motors used to control each finger independently, mounted on a control box connected to ISAC’s body. 4.An actuation system using 25-lb test fishing line that is run from the motors through cable housing to the fingers. 5.A microcontroller that controls the motors and receives feedback from the touch sensors on the hand. High-level control of the microcontroller is achieved by means of a serial port connection to a computer that contains a C++ Hand class. A Console application and a Windows Forms application that incorporate the Hand class are provided.

System Overview

Independent finger control was tested by running the hand through a number of different flexion and grasping tasks, including closing individual fingers in random order and performing grasping functions in random sequence. All these commands were successfully completed.

The functionality of the hand's grasping ability was assessed for each of the grasping functions by three different testing procedures involving variations in potential object weight, shape, and texture. The hand can hold textures ranging from a smooth plastic bottle to a plush animal. It can grasp sizes and shapes such as a credit card, pliers, and a Styrofoam cup. The hand can grasp objects with masses up to 500 g.

Durability of the fingers was tested through cyclic flexion and overextension- 500 cycles per finger. The finger/palm interface was tested through impact testing and was shown to be able to survive impact at 35 mph.

Functionality and Results

Software

There were a number of initial conditions applied to this project when we first undertook it. They were systematically met throughout the course of our work, in a manner that allowed us to finish well within budget:

1.The hand is an anthropomorphic right hand.2.The total mass is 200 g, well under the 1 kg limit. This was achieved by moving the motors and electronics off the hand and onto ISAC’s body.3.Through repeated testing, durability of the system was verified.4.Independent finger control and the requisite grasping motions are demonstrated.5.Feedback, via the touch sensors, is provided. The design has been tested and implemented on ISAC, and demonstrates full hand functionality.

Conclusion