How do I create a little robot

Building robots: courses at the UAS Technikum Wien

Whether as an industrial robot in automobile production or as a service robot that mows the lawn independently. Robots have a bright future and increasing demand. Technicians who understand how to design and build individual robots are in demand on the job market. Have you always been fascinated by technology and robots? Then studying mechatronics with a specialization in robotics might be just the thing for you. Don't you want to wait that long? Then you will find detailed instructions for building a robot here.

Bachelor and Master in Mechatronics / Robotics

The UAS Technikum Wien offers well-founded training as a bachelor's and master's degree (full-time or part-time) in the field of mechatronics. This imparts knowledge from the fields of mechanics, electronics, IT and sensor technology. You will gain an understanding of which sensory skills a robot needs to develop in order to carry out assembly, welding or palletizing tasks, for example. After a needs analysis, the robot can be programmed. The programming of industrial robots is taught in the first semester of the Bachelor's degree. Prior technical knowledge is not required for the course.

Program the motion sequences of industrial robots online

During the first semester you will get to know different types of robots. You will learn to define industrial robots, humanoid robots, mobile and service robots. How are they structured? What are the advantages and disadvantages of each? For what purposes can they be used and for which not?

The courses also clarify the question: What options are there for programming an industrial robot online or offline? There is a specialization in the industrial robots of the manufacturers ABB and Epson. In laboratory exercises, students learn to move these industrial robots and to create movement instructions. Industrial robots are usually tied to one location. Towards the end of their studies, students can develop moving robots. The aim is for the graduates to be able to develop solutions for the respective application as cost-effectively as possible.

How do you build a robot?

For many technology enthusiasts, there is something hypnotic about the movements of a robot. But how do you build your own little robot? Before you begin, there are three main questions that need to be answered:

  • What types of robots are there?
  • Which species is best suited for what?
  • What are the steps to start planning? What is to be considered?

There are various types of robots: industrial robots, service, care or entertainment robots.

In this manual we want to build a SCARA brand industrial robot. Industrial robots are used in production for various tasks in the areas of welding, assembly, packaging or painting. The SCARA robot is a special type of it. Its structure is reminiscent of a human arm. It is particularly suitable for pick and place applications. In contrast to other industrial robots, it has fewer axes. This allows a kidney-shaped work space to be covered.

Instructions for building a robotic arm

At the beginning of a robot project there is an idea. There are two approaches:

  • Either you already know what robott you want to build
  • or you know what the robot should do or what purpose it should fulfill

With this knowledge, you can search for templates on the Internet. Because a good robotics scientist knows that he / she doesn't have to keep reinventing the wheel. After doing the research, it should be clear:

  • what type of robot is being built
  • what he should do and be able to do
  • what this type of robot usually looks like / what the new robot might look like.

Double SCARA as a writing robot

For this tutorial, we decided to build a writing robot. With the pen as the end effector, the Double SCARA is able to produce drawings or letters. A stroke movement could be achieved by an additional linear joint on the end effector. She would realize the removal of the pen.

After the brainstorming process, the concept begins. Details such as the size of the robot or the production of individual parts do not yet play a major role here. It's more about giving the idea a shape: a sketch or a 3D model is sufficient. The following considerations are incorporated into the design of the concept:

  • Usage
  • Available components
  • Limitations and requirements

Accordingly, a rough plan is created for the writing robot, which can be adapted over time. Figure 1 shows the 3D design and explains its individual functions.

The following table lists the relevant individual parts of the 3D design:

number

descriptiondescription
1Frame with housingAn aluminum frame (consisting of 20x20 aluminum profiles) should serve as the basic structure of the Double SCARA.
2EnginesA total of three motors are required. Two motors are used to move the joints and the third to raise or lower the end effector.
3Sensors

Absolute encoders are required for the exact position detection of the Double SCARA. They prevent ambiguity and make initialization easier

4Articulated links

The robot limbs could be made in such a way that maximum mobility is guaranteed. Mutual collisions or restrictions are thereby minimized.

5End effector

The end effector consists of a motor, a translation and a pen. It is used to interact with the environment - in this case to write on a piece of paper.

6Controller and Motorshield

The controller and the motor shield are in their own housing which is mounted on the frame.

7care

The supply consists of a power supply unit. This is attached below the housing.

Once the sketch is ready, concrete planning can begin. The following questions must be answered:

  • How big should the robot get?
  • Do I already have components at home that I want to use?
  • Is there a price limit?
  • Where do I get individual parts or do I make them myself?

Manufacture individual parts yourself: Additive manufacturing

If you want to produce components yourself using 3D printing, one speaks of additive manufacturing. This means all possibilities to manufacture prototypes, models and end products quickly and inexpensively. These products consist of shapeless material, such as powder or liquids, which use chemical processes to create the product. However, access to a 3D printer is required for all processes.

A distinction is made between the following options (including advantages and disadvantages):

Powder printing

This printing process uses a specially treated homogeneous powder that is reinforced by composites. Its advantages are: Fast production, no support structures required and full-color models can be displayed. A disadvantage, however, is that the end products are only partially mechanically resilient if they are post-treated with composite materials.

Selective laser sintering

Different polyamide mixtures are used in laser sintering and hardened with a laser. The end products of this process can withstand mechanical loads. No support materials are required and they are flexible components. However, the materials here have a slightly rough surface and the manufacturing process takes a very long time.

Stereolithography

In stereolithography, plastics and resins are cured under UV light and heat. The end products here have a very detailed, fine surface. The process also has a high level of manufacturing accuracy. The disadvantage here is that the manufacturing process takes a long time and most materials are thermally limited.

Enamel stratification

Only thermoplastics such as PVC and ABS can be used with the melt layering process. This process is one of the most cost-effective and produces durable components. The disadvantage of this method is that only grooved surfaces are possible.

Polyjet process

Different photopolymer materials can be used in the Polyjet process. The method has a high level of accuracy and enables a very smooth surface. The disadvantage here is that the heat resistance of the components is limited when there are several materials.

In order to dimension the individual parts precisely, exact calculations are necessary for the construction of an industrial robot. The hobbyist usually foregoes this step and follows the motto "learning by doing". You can afford that in the private sector. In industry, however, calculations are inevitable. Calculations have to be made in order to select suitable motors for the robot arm movement. In the following example, for example, key figures such as acceleration and torque were calculated:

Example of calculations:

Once all parts have been ordered or manufactured, they can be assembled. The SCARA writing robot is based on an aluminum frame. The motor plates or the housing of the control are mounted on it. For a stable stand and the simultaneous fixation of the sheet to be written on, special feet are built in. The motors are then mounted on the motor plates as planned and the control cables are routed into the control cabinet with a suitable cable guide in the aluminum profile. The robot links are connected with M8 ball bearings and fixed to the motor shaft. The next step is to assemble the end effector and attach it to the designated location. This consists of a servo motor, gear and pen holder. The Arduino UNO microcontroller board is then attached to the location provided in the control cabinet.

The robot is standing, but is still a little lifeless. That's why we're taking care of the programming now. No matter which programming language you want to use, there are often enough interfaces and options to be able to program a robot even as a layperson. If you don't know what to do, specialist literature and the Internet can help.

Finally, the big test takes place. Does the robot do what it should? Do the individual parts move harmoniously like clockwork or is there still a problem in some places? After assembly, this phase will be the most time consuming as some errors are difficult to find. The following applies here: Testing and optimization are the key to success!