A product is to be made by gluing together two injection-moulded plastic components, A and B. It is proposed that a robot will perform the task using the following steps:
1. A pre-glued component A arrives on a conveyor belt to a predetermined location and the conveyor belt stops. The robot picks up A and inserts it into a fixture. The part is secured by vacuum suckers that pull A downwards into the fixture. Once the part is removed from the conveyor, the robot has to issue a binary signal to the conveyor to deliver another new component A.
2. Component B is supplied in a spring-loaded vertical stack which delivers the component to a fixed position from where it can be gripped by the robot.
3. The robot transports B and inserts it into component A. It pushes the assembly together with a force of 20 to 30 N.
4. Pressure is applied for 30 seconds and then the robot removes the complete assembly and places it onto a third conveyor. The robot has to issue a binary signal to the conveyor which increments its position to await the next completed assembly.
You are required to complete a conceptual design of the assembly cell paying particular attention to the interface requirements of all the control signals required to operate devices and ensure that the process operates effectively, whilst being able to detect all errors, for example the lack of a component.
Pay particular attention to the following:
1. Draw a plan view of the assembly cell which identifies all the sensors and devices
you plan to use.
2. Draw a block diagram of the overall system which includes all the sensors and
devices that are included in your design. The block diagram needs to be fully
annotated showing all input/output lines to the robot, all sensors, and devices.
Number each control line so that it can be specifically referenced in your program –
see item 6 below.
3. When designing your system ensure that it is capable of detecting all potential errors.
4. You may assume that a single axis force sensor is already connected to the robot
wrist and is capable of measuring the 20 – 30 N vertical force. This force sensor
utilizes strain gauges and the in-built bridge circuit and amplifier gives 0 to 12 volts
output corresponding to 0 – 40 N. An 8-bit ADC is to be used.
5. You must also assume that the robot has an I/O port with 10 inputs and 12 outputs.
6. Once you have designed your system you need to write a simple pseudo-code
program which illustrates how the robot will control the system – ie. How the
various sensors will be read into the controller, how external devices are controlled
(such as the conveyor belts), and how the force value will be detected and
The specified task and the requirements have been deliberately left vague to ensure that each student will interpret things slightly differently – this is a good thing! As a consequence each submission should be, and will be expected to be, unique.
The submission will require only THREE elements (additional text will NOT be
1. The detailed plan view.
2. The detailed block diagram – clear and precise.
3. The pseudo-code program. This program should use commands such as TestI,
WriteO, WaitI, GuardI. Ensure that ALL I/O line numbers correlate with those
assigned on your block diagram.