Agile robotic arm for vertical applications - Evaluation, design and development

Abstract

Existing pick and place robots are either heavy or have a limited workspace for
vertical operations. Since there is no robot today that are both light and have
a good vertical workspace, this leads to a gap in the market. With the use of
the laws of physics Cognibotics is trying to fill these gaps in the market, by
developing new fast and lightweight robots. These new robots are designed to
have as much of the total weight as possible close to the base. This will decrease
the moment of inertia which will help make the robots faster.

Cognibotics holds a patent with multiple different robotic arms that have the
possibility to have a vertical workspace. This thesis will focus on evaluate these
robotic arms and develop the robotic arm with the best opportunity to be fast,
lightweight and have a vertical workspace. The development will focus on the
overall layout of the arm, which includes the rods and joints. The sizes of the
rods will be selected and for the joints, bearing type and size will be selected.
The development of the joints will also include how the bearings should be
mounted.

In the patent, the robotic arm presented in fig. 9 is evaluated to be the best
option for further development. This arm is light, has a good weight distribution
(most of the weigh is close to the base) and fewer parts than the other arm, which
will probably make it cheaper. The original arm presented in the patent do only
have three DOF (degrees of freedom). The arm however can be modified to have
a fourth actuator at the end effector for the possibility to get the last DOF, which is needed for the application this thesis applies. Based on the selected robotic arm from the patent, two concepts where made. The first concept ”concept 1”, will probably be lighter and have a better weight distribution than the second
concept ”concept 2”. Based on this, the conclusion is drawn that ”concept 1”
is the best option.

For the selected concept, a CAD model was made. In the CAD model both
the rods and the joints are designed in greater detail. A total of five different
joints within the CAD model, were needed to be designed and developed. For
the development of the joints, a wide arrange of bearings are used. Some of
the more common bearings are angular contact ball bearings and tapered roller
bearings. In one of the more complex joint, spherical roller bearings are used.
For the development of the rods, a reach study was made. The lengths of
the inner and outer arms is selected based on this reach study. For a good
performance the size and profile of the rods was then investigated. Since one
rod is carrying almost the entire weight of the robotic arm, this rod need to be
bigger than the rest of the rods.

When the development of the robotic arm was complete, a crude cost analysis
of the robot was performed. This includes the total material cost for the
robot, which includes the cost for the rods, joints (with bearings), tool mounting
platform, motors, gearboxes and control systems.

Popular Abstract

Developing of a new robotic arm

Even though there exists a wide variety of different industry robots used for different purposes, there are many unexplored robot types. When a robot pick up an object at one point and place at an other this is called a pick and place robot. When looking
at pick and place robots a trend can be seen that the existing robots are either heavy and slow but have a good reach vertically, or light and fast but with a limited vertical reach. By developing a new robot, new application areas can be found, which could
be a part of the evolution of the industry.

When starting to develop a new kind of robot type it is important to know in which areas the market can be improved. A new area where a new kind of robot could fit can here be found if the properties of the two robots above can be combined. If this is possible this new robot would have the best of two worlds, where it would be light and fast but also with a good vertical reach.
This new robot could help improving the industry in many ways, where one example would be as a palletizing robot.

As a base for this new robot, one patented robotic arm was selected and used. This robotic arm would give a good baseline for the kinematic principles for the new robot.

In order for this new robot to fulfil the wanted properties, light weight materials was used. Carbon fibre is a material with many suitable properties for this application, this since it is very stiff but do also have a very low density. To further decrease the weight of the robotic arm almost all electric motors and gearboxes would be located on the base of the robot. This would also give a more preferable weight distribution which would help increase its speed even further.

When developing this new robot the main focus was on the actual robotic arm, which includes the rods and joints. A robotic arm includes many parts which are in need of dimension, some of them are the carbon rods and the bearings. All these parts need to be verified in some way to make sure they are big enough. For this, FEM was an important tool, since it would provide a good amount
of data, which in turn could be evaluated and used for the developing.

This new robot can have the potential to help increase the efficiency for many different companies. It could be used in the industry when loading different products on pallets or it could help in warehouses to fill containers with goods that are going to be transported to different locations. These are just a few examples of where the robot could be used.

• author: Gren, Rasmus
• supervisor: Rikard Hjelm
• organization: Machine Elements
• course: MMEM01 20231
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Robotic arm development, HKM, Kinematics, Product development
• language: English
• id: 9124135
• date added to LUP: 2023-06-13 08:53:24
• date last changed: 2023-06-13 08:53:24