MENG306

Supervised by: Dr. Ahmed Askar and Engr. Marwa Albadawy

Project report

Simple robotic arm

Team members:

Name ID
Moustafa Aly 19105936
Ahmed Elmenyawe 202000548
Eslam Eldeeb 202000346
Yahia Elmelegy 221000224
Karim
Malek Hassane 221000315
 MENG306

Supervised by: Dr. Ahmed Askar and Engr. Marwa Albadawy

Project report

Simple robotic arm

Team members:

Name ID
Moustafa Aly 19105936
Ahmed Elmenyawe 202000548
Eslam Eldeeb 202000346
Yahia Elmelegy 221000224
Karim
Malek Hassane 221000315
1. Revised Sections

 Incorporate Feedback:

 Based on the feedback received on the previous report, we revised the following sections:

 Introduction: Clarified the purpose and applications of the robotic arm.

 Mechanism Function: Expanded the discussion on alternative mechanisms.

 Design Objectives and Constraints: Added specific measurable criteria.

 Design Conceptualization: Enhanced the justification for the selected design.

 Motion Transmission: Provided more detail on the motor selection.

2. Mechanism Function

 Functions of Various Mechanisms:

 The robotic arm can perform various tasks such as pick-and-place operations, assembly, and
welding. Alternative mechanisms that can achieve similar functions include:

 Cartesian Robots: Utilize linear actuators to move in straight lines along the X, Y, and Z
axes.

 Innovative Motion Creation:

 To create the intended motion, we explored the use of:

 Servo Motors/DC Motor: For precise control of joint angles.

 Cable-Driven Systems: To reduce weight and increase flexibility.

3. Design Objectives and Constraints

 Design Objectives:

 Minimum weight: The arm should weigh less than 5 kg for easy mobility.

 Minimum power: Power consumption should not exceed 50W.

 Cost-effectiveness: Total cost should be under 1500EGP.

 Design Constraints:

 Minimum force required: Each joint must handle a minimum load of 2 kg.

 Required cycle time: The arm should complete a full cycle (pick and place) in under 30 seconds.

 Available motor power: The total power supply must be compatible with standard 12V motors.

 Assumptions:

 The robotic arm operates in a controlled environment, minimizing external disturbances.

 The payload is consistent and does not exceed the specified limits.

4. Design Conceptualization
 Creative Thinking:

 Design requirements were gathered through brainstorming sessions, focusing on

flexibility, precision, and ease of control.

 Considered various configurations (e.g., 2-DOF, 3-DOF) to achieve the desired range of
motion.

 Concept Selection:

 After evaluating several designs, and calculation and doing the CAD design we reached
that on the CAD model we had 4 DOF and the concept design we calculated 3 DOF so to
make it simple we selected a 3-DOF robotic arm with three rotational joints. This design
provides a good balance between complexity and functionality.

Degree of freedom:

M =3 (L−1)−2 J 1−J 2
M: degree of freedom or mobility

L: number of links

𝐽1: number of full joints

𝐽2: number of half joints

In our robotic arm we have 4 links, 3 joints.

M= 3(4-1) - (2*3)- 0

M=3 D.O.F

 Justification: The selected design allows for a wide range of motion, is cost-effective,
and is easier to control with standard servo motors.

 Schematic and 3D Model:

 A schematic diagram of the robotic arm is included below:
  A 3D model has been created using CAD software (e.g., SolidWorks) and is shown below:

5. Motion Transmission

 Transmission Mechanism:

 The robotic arm is driven by three servo motors, one for each joint. Each motor is
directly connected to its respective joint, allowing for precise control of the arm's
position.

 A gearbox is not required as the servo motors provide sufficient torque and speed for
the intended tasks.

 The selected servo motors (e.g., MG996R) have a torque rating of 9.4 kg/cm, which is
adequate for handling the load.
6. Synthesis

 Graphical Techniques

 In this study, kinematic analysis was performed using graphical methods to determine
the positions of the robotic arm's end effector based on joint angles.

 Geometric Kinematics

 Geometric kinematics provides an intuitive approach to analyze the motion of robotic

arms by utilizing basic geometric principles. This method focuses on the relationships
between the joints and links of the robotic arm, allowing us to calculate the position of
the end effector based on the angles of the joints and the lengths of the links.

 Link and Joint Representation:

 The robotic arm consists of two links, each with a length of (L_1) and (L_2), connected
by two revolute joints. The angles of these joints are denoted as (theta_1) and
(theta_2).

 Position Calculation:

 The position of the end effector ((x, y)) can be calculated using the following
trigonometric equations:

x=x 2=l 1 cos ( θ1 ) +l 2 cos ⁡(θ1 +θ2 )

y= y 2=l 1 sin ( θ1 ) +l 2 sin ⁡( θ 1+ θ2)

Where l1 and l2 are the lengths of the two links. The orientation of the tool frame
relative to the base frame is also given by the direction of the cosines of the x2 and
y2 axes with respect to the x0 and y0 axes.

x 2 ⋅ x 0=cos ( θ1 +θ2 )

x 2 ⋅ y 0=−sin(θ 1+θ 2)

y 2 ⋅ x 0=sin ⁡( θ1+ θ2)

y 2 ⋅ y 0=cos ⁡(θ1 +θ 2)
These four equations can be combined to obtain an orientation matrix.

|x2 ∙ x0
x2 ∙ y ||
y 2 ∙ x 0 cos ⁡(θ 1+θ 2) −sin ⁡(θ 1+θ 2)
=
y 2 ∙ y 0 sin ⁡(θ 1+θ 2) cos ⁡( θ1+ θ2) |
 By substituting the lengths of the links and the joint angles into these equations, we can
determine the exact position of the end effector in a 2D plane.
  Visualization:

 A graphical representation of the arm was created to illustrate how the end effector's
position changes with varying joint angles. This visualization aids in understanding the
workspace of the robotic arm and the impact of each joint's rotation.

 Inverse Kinematics:

 To determine the necessary joint angles to reach a specific target position, we applied
basic trigonometric relationships. This involved rearranging the position equations to
solve for (theta_1) and (theta_2), facilitating effective control of the robotic arm.

 Advanced Techniques:

 Simulations using software (e.g., MATLAB) to visualize the arm's motion and validate the
design parameters for future work

Conclusion

 This report outlines the design and functionality of a simple robotic arm capable of executing
pick-and-place tasks. By incorporating feedback and engaging in creative design processes, we
developed a robust mechanism that meets the specified objectives and constraints. Future work
could involve integrating sensors for feedback control and enhancing the arm's capabilities.

References

 Robotics: Control, Sensing, Vision, and Intelligence by John J. Uicker Jr.

 Introduction to Robotics: Mechanics and Control by John J. Craig

 SolidWorks User Guide