Detailed Report on 5-Dof Light-Weight Robot Arm Design & Control

This report details the design, modelling, and control of a 5-degrees-of-freedom (5-Dof) light-weight robot arm, named PUL5AR, for aerial manipulation tasks using unmanned aerial vehicles (UAVs). The project focused on creating a compact and portable robotic arm suitable for military and civil sectors. The report outlines the objectives, including designing, modelling, and controlling the robot arm, manipulating existing mechanisms, validating dynamic models, and maintaining a light-weight design within a specified timeline. Key activities included analyzing existing robotic arm models, identifying limitations, and implementing design modifications to address kinematic coupling issues between the UAV and manipulator motion. The innovative aspects of the project involved relocating motors to the base of the arm to minimize static torque and developing a folding design for landing maneuvers. The report also discusses the challenges encountered, such as weight constraints and communication issues, along with the solutions implemented, including using a honey comb structure and incorporating a communication protocol. The project leveraged 3D printing for mechanical parts and experimental testing to validate the arm's functionality.

COMPETENCY
DEMONSTRATION REPORT
Career Episode 1

CE 1.1 Project Information
Name of the project: Designing, modelling & control of 5-Dof light-weight robot arm
for Aerial manipulation
Location of the project: [PLEASE FILL]
Project Duration: [PLEASE FILL]
Organization: [PLEASE FILL]
Role and Designation during the time: Team Leader
CE 1.2 Project Background
CE 1.2.1 Characteristics of the project
I proposed the design, modelling and control of the 5 degrees- of – freedom light- weight
robot manipulator that can hold objects of certain specified weights. I named the proposed arm as
PUL5AR (Prisma Ultra-Light-weight 5 ARm) in manner to execute the manipulation of the tasks
furnished on the board of the lading and vertical take – off unmanned aerial vehicle. I kept the
proposed model light and compact in manner to keep it portable and applicable wherever the
industries want to use it. I considered the military and civil sectors where UAVs (Unmanned
Aerial Vehicles) are being most applicable and proposed a manipulated model that is much
efficient and effective. The project needed a group of team members who have well
understanding on the facts relate to the design and application of the robotic arms.

CE 1.2.2 Objectives developed for the project
I developed the following objects in manner to take in account that every team member
will follow the following objectives in manner to be focused and concentric towards
accomplishing the final goals of the project:
To design, model and control a 5 degrees – of – freedom light – weight robot manipulator
To manipulate the existing mechanism of the robotic arms
To validate dynamic model and control schemes
To keep the project compact and light – weight
To accomplish the project within the specified timeline
To deliver the productive project
CE 1.2.3 My area of work
I investigated the various tasks involved while executing the project that includes
inspection, guarding or remote sensing and the passive interaction with the environment. I
analysed that the kinematic coupling between the UAV altitude and the manipulator motion are
the major issues associated with the application of the previous models of robotic arms. I
managed to eliminate these problems through manipulating the existing design through
designing of the differential joint at the base of the robotic arm. I relocated the motors at the base
of the arm that was helpful in destabilizing the effect on the UAV attitude raising because of the
static torque occurring through the COGs misalignment has been minimized. I manipulated the
folding design mechanics of the robotic arm through allowing the robot to be capable of moving
in five directions.

CE 1.2.4 Project Group
CE 1.2.5 My responsibilities throughout the project
I was responsible for analysing the existing model of the robotic arms and recognize the
sectors those have been influencing the effectiveness and efficiency of the robotic arms. I
managed the entire team’s role and responsibilities along with the regular project documentation
and monitoring that was helpful in keeping them motivated towards accomplishing the objectives
and goals of the project. I implemented the application of the aerial manipulation with UAV
endowed with the robotic arm in manner to develop the new design mechanics for the PUL5AR.
I had to manage the dimension and weight of the robotic arm and so adopted the following
specifications in manner to achieve the respective objective related to the size and weight:
 Arm weight / payload: 250 g / 200 g.

 Retain the possibility to execute VToL.
 Arm maximum extension: 300 mm
 Kinematics and dynamics decoupling
CE 1.3 Distinctive Activity
CE 1.3.1 Comprehending the theory of the project
The design of the robotic arm has been kept light- weight and compact and has been
designed in a manner that it can be applicable n folding itself during the instances of the landing
manoeuvres. The proposed design has been developed considering the constraining of the centre
of gravity closer to the base of the robotic arm vehicle that was helpful in reducing the static
unbalancing and total inertia of the system. Considering the developed electronics,
communication library, control schemes, and validation of the dynamic model, experimental
tests have been carried out those have been implemented within the proposed design of the
robotic arm. The proposed model has been developed considering the constraints such as aerial
robotics including limited energy storage and payload.
CE 1.3.2 Engineering knowledge and skills applied in the project
I utilized six actuators within the developed arm that include two digital servomotors and
four DC motors for the gripper and last joints, and first joints respectively. I positioned the last
two DC motors at the initiation of the second joint and two DC motors had been included within
the arm’s base. In manner to allow the motion among the robotic arm and allowing the UAV roll
– pitch’s active compensation on the end-effector position of the manipulators, I designed the
first two joints as the differential joints. Reduced the inertia of the arm through positioning the

first two motors inside the base. Moreover, I adopted the timing belts those were effective in
allowing the relocation of the other two motors within the base of the first link. I developed the
following graph considering the gathered results:
Figure 1: “Variation of the position of the arm’s CoG (magenta) with respect to
different joint configurations corresponding to the gripper centre (red) moving along the
vertical (left) and horizontal (right) axes”

Figure 2: Diagram of the ratio of the distances of the robot’s CoG pb CoG and of the
gripper position pbe, from the robot base, with respect to
∥pbe
∥.
CE 1.3.3 Accomplishment and task performed
I had to manage and motivate the team members towards the proposed design in manner
to propose and develop a sophisticated model of the robotic arm that can be used within the
industries to lift material. I analysed the existing features and mechanism of the robotic arms and
recorded the existing issues those are restricting the efficiency of the application and
manipulated those designs in manner to be applicable for the industries in far better ways. I
proposed the new model with various manipulations and named it as PUL5AR through targeting
the elimination of the existing problems. I proposed and evaluated the dynamic model of the
robotic arm:
Figure 3: The Joints

I evaluated the frames and the DH parmeters those could be described in the following
table:
Link ai αi di vi
1 0 π/2 0 v1
2 150 0 0 v2
3 88 - π 0 v3
4 0 π/2 0 v4
5 0 0 -60 v5
The position vector within the “joints have been assigned along the gripper approaching
axis and zb1 (q) led to the direct kinematics as:
Differentiating this equation with respect to time following equation can be derived:
JA(q) is nothing but the Jacobian Matrix and the detrminant can be computed as:

V3 can be calculated as:
These caculations helped in developing the following dynamic momdel:
The inertial parameters can be demonstrated as following table:
CE 1.3.4 Identified issues and their solutions
1.3.4.1 Issues
I identified that the maximum weight constraint resulted in limiting electronics and the
mechanical design as the weight per payload ration had been 1.25 that was completely different
from typical robots of the industries that is approximately 20. The communication between the

robots and the centralized system was another concerning sector that needed to be eliminated
while delivering the project.
1.3.4.2 Solutions
I used the honey comb structure for the robotic arm design that was helpful in reducing
the total weight and thus, making it applicable for the industries. In manner to identify the
functioning, I delivered the FEM analysis that was helpful in identifying and proposing better
structure of the robotic arm. I incorporated a communication protocol that was helpful in
commanding the robots with the hosted computer endowed of a USB.
CE 1.3.5 Plan to produce creative and innovative work
I used 3D printing mechanism for producing the mechanical parts and proposing the
specific model of the light – weight robotic arm that was composed through acrylic monometer.
The setup was not the only factor to develop the project successfully as the landing and the
vertical take-off functioning “(VToL) UAV with similar payload and computational board
endowed with a USB.” Considering all these factors, I carried out the experimental testing
through using the communication and control software those have been specifically written for
the proper and effective functioning of the arm.
CE 1.3.6 Collaborative work
The project as successfully delivered and evaluated through the contribution made by
every team member as every team member had been contributing their specified sector of the
work in manner to ultimately make the project productive. I implemented my mechanical
engineering skills for the development of the specified mechanic design in manner to make the
project different from the previous models. I divided the project in different phases that includes

evaluation of the existing models, identifying the necessary modifications, developing the design
of the new robotic arm, delivering the mathematical calculations, and evaluating the proposed
design. I managed the roles and responsibilities of every team member involved in the project.
CE 1.4 Project Review
CE .4.1 Project Overview and My contribution to work
I proposed the design of the robotic arm that can function in five directions and manage
the objects within the industries in efficient and effective manner. I was responsible for analysing
the existing features and mechanisms of the robotic arm and assuring that the every concerning
sectors have been touched and analysed. I managed to implement the manipulation in the
existing systems and assure that the derived model is capable of fulfilling the respective
outcomes after eliminating all the issues. I controlled and evaluated the growth and development
of the project through continuous monitoring and regular documentation that was helpful in
accomplishing the objectives of the project.