Prototype SCARA pick-and-place arm with a controller designed for AI learning, under a Thai government-funded project in 2018

How the brief came about

This prototype robot arm picks and places workpieces at positions that technicians with basic skills can set themselves from a screen. The brief was a robot arm whose machine price and maintenance costs are within reach of SMEs. The project report states that the target group had a problem of reliance on manual labour. For small and medium-sized factories, investing in a robot arm means considering the machine price, the maintenance costs and the people who can set up the machine.

This work falls under the government's 2018 technology product development program for import substitution, which supports developing technology products domestically instead of importing them. The private company that will use the machine co-invested in the project, while we designed, built and tested the prototype.

Requirements and constraints

The prototype had to meet the project's requirements, within a contract period of 8 months. The main requirements and constraints are as follows.

• A 4-axis SCARA robot arm (1 set), with a working radius of at least 400 millimetres and a workpiece load of no more than 1 kilogram
• Technicians, electricians or staff with basic computer skills must be able to set it up, without a specialist
• The project handbook specifies features for the robot arm to learn, with AI, to pick workpieces of similar size, shape and weight, to be controlled over a LAN (the factory's internal network), and to store its operating status history on a Cloud Server (an online data storage machine)
• The robot arm rotates quickly and with force, so it needs a safe area around its working radius and warning signs to keep people and objects away
• Contract period of 30 March – 30 November 2018, with progress reports, a final report, and an operation and maintenance manual

How was this prototype robot arm designed so that technicians who are not robotics specialists can set it up?

Users set up the robot arm from a software screen on a computer by adjusting the angle of each axis joint, then check its posture in the simulation system (Simulation) with a 3D model of the arm before running the real machine. We chose this approach because the project's target users are technicians with basic skills, not robotics specialists. The steps in the operation manual are as follows.

1. 1

   Install the controller on the robot arm

   Connect the controller to the robot arm, then open the software and load the arm's 3D model into the system.

2. 2

   Set the movement positions

   Enter setup mode to define the robot arm's postures and positions for each job by adjusting the angle of each axis joint on the screen.

3. 3

   Test with the simulation first

   Command the robot arm to move in the simulation to check its posture before running the real machine.

4. 4

   Run the real job

   Once the posture in the simulation is correct, command the robot arm to pick the workpiece from the set position.

Deliverables

We delivered 1 robot arm prototype set, with documents and transfer of operating know-how as set out in the contract. The delivered items are as follows.

• A 4-axis SCARA robot arm mounted on a control cabinet using an NVIDIA TX1 processing board
• Software for setting positions and simulating the operation with a 3D model
• Progress reports and a final report
• Operation and maintenance manual
• Transfer of operating know-how to the private company participating in the project
• Testing the robot arm program with a steel stamping press at a metal stamping factory

Verifiable prototype assessment results

The project's assessment form dated 15 March 2019 records 3 results for the 4-axis SCARA robot arm prototype: the machine was fully assembled as a complete machine, its operation could be tested according to the specified functions, and it had a safety protection system. The form also includes recommendations to adjust the earth wire (ground) and signal lights.

After the assessment, we placed the sponsoring agency's sticker on the machine and filmed a demonstration clip of it working. The on-site testing carried out consisted of testing the robot arm program with a steel stamping press. Use for picking workpieces on a production line requires further testing with real workpieces, and the robot arm's command circuit and control screen have items for improvement after the project closed. This page reports only results backed by documents.

What we learned

This work offers 3 principles for developing robot arm prototypes and prototype machinery.

• Separate tested features from target features. In this work, AI, control over a LAN and the Cloud Server are listed as features in the handbook but have no test results, so prototype handover documents should state clearly which items have been tested.
• A robot arm prototype must pick real workpieces at a real machine before it can be called ready for use. Testing the program with a steel stamping press is a first step; it is not yet the same as picking workpieces on a production line.
• Electrical and safety systems are part of the design work from the start. The technical recommendations in this work's assessment concerned the earth wire and signal lights, while the safe area around the robot arm's radius was part of the project's risk assessment.

How can you apply this approach to your project?

If you want to try a robot arm on your own pick-and-place work, or develop a machine prototype in a research project, you can use the same approach as this case: set postures from a screen, simulate the operation before running the real machine, and deliver with a manual and transfer of operating know-how. What needs adjusting is the robot arm's specification, when your workpieces are heavier or further away than this prototype was designed for.

• Clearly specify the workpieces the robot arm will pick, including size, shape and weight
• Prepare the installation area, electrical system and earth wire before testing
• Define a safe area around the robot arm's working radius and put up warning signs
• Agree the deliverable documents from the start, such as reports, an operation and maintenance manual, and technology transfer