In today’s modern world the development in robotic technology has played an important role in many fields. In the manufacturing field, robot development has focused on engineering robotic arms that perform manufacturing processes. In space technology, the robotic arm with rover has automated space exploration and research. If we consider the military field the robotic arm has relieved the technicians of danger when it comes to deactivation of bombs.

This project is to design and construct Robotic arm with Rover, capable of being programmed from an external device run by a microcontroller. The entire operation is being manually controlled to obtain the desired results.

1. The robotic arm was designed to resemble the human arm that is able to grip, pick and place various objects.
2. The arm is a 5 axis robotic manipulator consisting of a rotating base, three links and a gripper. The five axes consist of the following:
· Shoulder, elbow, wrist (vertical movement)
· An axis at the base (horizontal movement)
· Finger (gripping movement)
3. The whole robotic arm along with the rotating base is placed on a rover which exhibits forward, backward, left and right movements.

We have been successful in designing the mechanical structure of the robotic arm along with the rover and it is operating as planned.

SYSTEM DESCRIPTION

Project is to design and construct Robotic arm with Rover, capable of being programmed from an external device then run by its own controller ,and can be manually controllable.
The main component in terms of visibility and end result is the mechanical and servo motor . The arm itself has five degrees of freedom and has gripper and the rover has two geared DC motors. And the rover has Forward, Reverse, Left and right movements.

Robotic Arm

The arm has five degrees of freedom and five servo motors, one for each joint except for the farthest vertical joint from the gripper, known as the “shoulder”(shoulder has 2 servo motors).

Degrees of Freedom (DOF)

The degrees of freedom, or DOF, is a very important term to understand. Each degree of freedom is a joint on the arm, a place where it can bend or rotate or translate. We can identify the number of degrees of freedom by the number of actuators on the robot arm. Now this is very important - when building a robot arm. Because each degree requires a motor, and exponentially complicated algorithms and cost

Description of Arm

The shoulder joint requires reinforcement by two servo motors in order to increase the torque driven through the joint, to counteract the weight of objects in the gripper. The other three motors each drive their own joint. There is a, a vertical shoulder joint (driven by two coupled motors), a vertical elbow joint, a vertical wrist joint, and a motor that drives the opening and closing of the two-fingered gripper. In total, it has a total of five degrees of freedom. rotational base joint is driven by geared dc motor.

Robot Workspace

The robot workspace (sometimes known as reachable space) is all places that the end effectors (gripper) can reach. The workspace is dependent on the DOF limitations, the arm link lengths, the angle at which something must be picked up at, etc. The workspace is highly dependent on the robot configuration.

DESIGN, CONSTRUCTION AND ASSEMBLY OF THE ROBOTIC ARM:

The robotic arm was designed to resemble the human arm that is able to grip, pick and place various objects. The design of robotic arm involves few major components which include the rotating base, shoulder, elbow, wrist and gripper The arm is the main structure consisting of a mechanical structure, servomotors, and power supply. The arm is a 5 axis robotic manipulator consisting of a rotating base, three links and a gripper.
The five axes consist of the following:
• Shoulder, elbow, wrist (vertical movement)
• An axis at the base (horizontal movement)
• Finger (gripping movement)
The main considerations taken during the design process was to design a robotic arm that assembles the human arm, able to stand alone, size should be similar and not too bulky,light and the overall cost should be low.

The design of the rotating base:

It consists of metal plates attached to the left and right side. The is hollow to reduce material usage and the overall weight. The base of the robotic base is attached on a geared dc motor to provide base rotation with the help of wooden wheel . This is needed to support the entire weight of the robotic arm and objects that is gripped with the gripper. The servo motors used for movements of the arm are able to rotate to a maximum 180 degrees.

The design of the shoulder:

The design of the shoulder fully assembles the human arm. The metal plates used to connect the left side and right side is designed to have smaller dimension that does to cover the entire length of the sides. The movement of the shoulder is supported by two large-scale servo motor working together simultaneously. These motors are also able to move 180 degrees.

The design of the elbow:

As for the elbow, it is only supported by a single servo motor as the weight it need to support is much reduced. It only needs to support the wrist and the gripper and it is mounted to one side of the elbow assembly. The other side is supported by a smooth spring attached to the shoulder Spring Contact it does not cause much friction and unwanted noise that might appear when two parts collide with each other.

The design of the wrist and the gripper:

The wrist is made up of standard servo motors which One more servo is attached side by side are to move the wrist by 90 degrees and the servo attached at the top is to control the movement of the gripper. The wrist was designed as light as possible as it is supported by standard servos.

Fabrication and construction of the robotic arm

The material used to fabricate the body of the robotic arm was chosen to be aluminum as it is a light weight metal, rigid, cheap compared with stainless steel and easy available in the market. It is also resistance to wear and rust. Another important point why aluminum was chosen mainly because it is easy to fabricate as the components of the robotic arm require a lot of bending and hole drilling process. The thickness of the aluminum was chosen to be 1.5mm thick.
This thickness of material is common and the price is reasonable. This thickness is suitable for the robotic arm and after bending and drilling, the material is still rigid and strong. For the fabrications of the individual parts design ideas and dimensions are provided to the fabricator to manufacture the parts .
The construction and assembly of the body of robotic arm consists of few major components which include aluminum pieces, screws, nuts and washers. The construction of the robot arm begins with base when the arm is mounted and during rotating operations. Then, hole a drill at one side to allow the servo motor wire to go through. Then, the individual part used to form the rotating base is assembled together using screws, nuts and washer. Servo motors are attached to the body using servo horns that are provided with the servos.
Next, the shoulder components are assembled together before mounting to the rotating base. This is followed by assembly of the elbow, wrist, and gripper components. Then all servo motors that are attached to the components are turned manually to determine the maximum limit. It is then manually positioned to the middle position. Finally, all components of shoulder, elbow, wrist and gripper are secure into position. As the motors are placed at their centre position, during the placement of the shoulder, elbow and wrist, the parts are ensure to stand horizontally so that after attachment, the robotic arm is able to move to the right and left position by 90 degrees each side.
As for the gripper, the parts are tightened with enough force to allow the pieces to move freely without friction and unwanted sound but enough to hold the parts in place. The final step is to mount the gripper to the wrist.

Arm specifications:

Five Axes of motion:

Base Right / Left:350 degrees

Shoulder:120 degrees

Elbow:90degrees
Wrist:90 degrees

Gripper Open & Close:50 mm ( 2 in )
Dimensions:

Max Length Outwards:360 mm ( 14.2 in )
Max Height Upwards : 510 mm ( 20.1 in )

Max Lifting Capability:130g ( 4.6 oz .)

Power Source:+6volts

Power Consumption (per each Unit): 700mA (no-load)

Weight : Robot Arm Approx .1,050g

Height:405mm(16 in)

Servo Motor Specification:

fig:servo motor

Detailed Specifications:

Control System:+Pulse Width Control 1500usec Neutral

Required Pulse:3-5 Volt Peak to Peak Square Wave

Operating Voltage:4.8-6.0 Volts

Operating Temperature Range:-20 to +60 Degree C

Operating Speed (4.8V):0.19sec/60° at no load

Operating Speed(6.0V):0.15sec/60° at no load

Stall Torque (4.8V):42 oz/in (3.0 kg/cm)

Stall Torque (6.0V):49 oz/in (4.5 kg/cm)

Current Drain (4.8V):7.4mA/idle, 160mA no load

Current Drain (6.0V):7.7mA/idle, 180mA no load

Dead Band Width:5usec

Operating Angle:40° one side pulse traveling 400usec

Direction: Clockwise/Pulse Traveling 1500 to 1900usec

Motor Type: Cored MetalBrushPotentiometer Drive: 4 Slider/Direct Drive

Bearing Type:Top/Resin Bushing

Gear Type:Nylon360

Modifiable:Yes

Connector Wire Length:11.81" (300mm)

Weight:1.52oz (43g)

Discussion on Mechanical structure design:

It was decided that servomotors be used to actuate all joints because of their ability to hold their position. However, the limited amount of torque the servos can provide presented some serious limitations in the link design. The links needed to be reasonably long to maintain the arm‘s functionality, but at the same time they needed to be as light as possible. Aluminum sheets found to be the appropriate material for link construction due to their lightweight, easy bending and cutting properties While the conceptual design was easy, the actual implementation proved to be the most challenging part of the project. There were several different designs attempted and modifications made to the links throughout the project. The initial design was very light but at the same time, very weak. Since the servomotors are the heaviest component of the arm, all the motors were placed at the base to reduce the weight. These motors used sprockets to drive the gears that are fixed to the arms at the shoulder, the elbow, and the wrist. We found that without proper and more advanced tools, this design could not be done

Mobile Manipulators (Rover):

fig:Track belt and wheel

A moving robot with a robot arm is a sub-class of robotic arms. They work just like other robotic arms, but the DOF of the vehicle is added to the DOF of the arm. We have a differential drive robot (2 DOF) with a robot arm (5 DOF) attached that would give the robot arm a total sum of 7 DOF

Track belt and Track Wheels:
Track belts used for rover.which provide better grip.is made of ruber . it has dimention of 1"width and 2' length.


DC Motor Specification:
Control System: H-Bridge Circuit

Operating Voltage: 3.0-12.0 Volts

Operating Temperature Range: -20 to +60 Degree C

Operating Speed (12V): 100RPM at no load

Current Drain (12V): 600mA no load operating

Direction: Clockwise/Anticlockwise

Motor Type: Geared DC
Gear Type: Metallic

Robotic Arm with Rover(video)

Here is the Video captured during demonstration