1 Introduction
You are required to provide a sensor/instrument design to fulfil the measurement requirement as set out in Section 3 below. Before going to that section, you are encouraged to understand the requirements of the assignment first, which follow in Section 2.
Ideally the design will be both fully convincing, i.e. fully explained and justified by analysis, and also complete such that a prototype might be immediately manufactured from the information provided.
This assignment is to be delivered in report format as a single .PDF submission.
General Requirements
Feedback and Assessment
To manage the development of your design this assignment will be assessed in two stages, namely:
Assignment 1 - ‘Preliminary Design' , due as shown on the cover page, but preferably sooner, and worth 100 marks. Your submission will be returned to you with comments typically within one working week of receipt of your submission.
Assignment 2 - ‘Final Design' , due just prior to the examination period, as shown on the cover page, and worth 300 marks (This will be assessed during the exam period, where you may not receive feedback in time for the exam.)
Note that each assignment has it's own marking rubric.
The marks for the two parts will be combined and an overall achievement of 200 (of the 400 total) is required for satisfactory completion of the aggregate assignment. You are encouraged to read the course specifications for ELE4109 to understand all the conditions of the course. You should also pay particular attentention to the requirements to pass the course being:
Requirements for student to be awarded a passing grade in the course: To be assured of a passing grade, students must demonstrate, via the summative assessment items, that they have achieved the required minimum standards in relation to the objectives of the course by:
(i) satisfactorily completing the examination and assignments; and (ii) obtaining at least 50% of the total weighted marks available for all summative assessment items.
Requirements of your Prelimenary Design Study
The following requirements are for Assignment #1 of the pair of assignments for this course.
As set out in Section 3 below, the use of a hinged ‘impact plate' has been suggested to meet the measurement requirements. However there may be other methods / sensing arrange- ments which will result in a better instrument design for this purpose. Therefore there are three requirements of this preliminary design study:
A. A general assessment of possible sensing schemes using the Mea- surement Process Algorithm (MPA). This should yield a comparison table of the advantages / disadvantages / limitations of each.
B. An outline design / feasibility study of the suggested ‘impact plate' sensing scheme, i.e. how the plate can be transduced to yield the required measure- ment information. Obviously there are several options available. Remember that use of the Measurement Process Algorithm may be appropriate.
C. Preliminary design decisions for the final measurement system.
Obviously the quality of the feedback you receive to assist with your development of the final design will depend directly on the thought and analysis put into these initial design studies2.
Requirements of your Final Design, Assignment #2 2017
The following requirements are for Assignment #2 of the pair of assignments for this course.
This assignment will follow on from Assignment #1 and expand on your preliminary design decisions leading towards the final measurement system. As stated above, a complete and convincing instrument design is required. This will include at least the following:
- An explanation and justification of the sensing scheme chosen. This may be ‘impact plate'-based, or any other means. Obviously this will be based on your initial submission.
NOTE that this is not an exercise in "picking the right answer". There will be several and perhaps many techniques (and methods of implementation) which will meet the requirements of each Assignment.
- A full design of the sensor(s) and transducer(s) employed, i.e. shape, size, material, arrangement, components (if any *3), installation, housing/protection, etc. You may need to make assumptions about the measurement situation, or if particular features are critical, specify certain requirements.
- An analysis of the performance of the sensor(s) and transducer(s) in this situation, i.e.:
- static and dynamic responses,
- signal and energy flows,
- loading effects,
- external influence effects, - etc. (as appropriate).
- An explanation and justification of the signal processing required to pro- duce the output required.
- A full design of the signal processing components from transducer inter- face to output interface. Both analogue and digital electronics must be designed, including EMI/RFI protection, grounding considerations, etc., and at least the ma- jor/critical components selected (*refer footnote 3). The internal details of any mi- croprocessor or DSP hardware required may be omitted but components should be specified and, of course, the software written and explained. Remember that as any software which forms part of the instrument operation will be required to operate in ‘real time' therefore runtimes. etc., will be important. Likewise the details of any printed circuit board design, power supplies and cases, housings, etc. may be omitted unless you feel they are unusual or particularly critical to your instrument design.
- An assessment of overall performance, including:
- calibration requirements and methods;
- stability;
- drift; and
- general reliability.
- An assessment and discussion of problems and limitations (if any!) with your design.
- Modelling as appropriate for any (all?) of the above aspects of the design.
- Commercial and managerial aspects such as costs, resource requirements and development times are not specifically required but credit will be given for these if they are significant and strictly relevant.
The Assignment - Design of a Grain Flow Monitor
Introduction
The construction of a large grain storage silo (nominal 5000t design capacity) is being planned. Management of the quantity of grain stored in obviously important, therefore it is required to monitor, i.e. continuously measure, the mass of grain. Because of the large size of the silo it is considered impractical to measure the total mass of grain directly (e.g. via load cells in the silo support structure), hence it is proposed to measure the instantaneous mass flow rate of the grain entering the silo and derive the cumulative mass of grain from these measurements. (Separate measurements will be made of the grain removed from the silo.)
It is proposed that the grain will enter the top of the silo via a feed hopper as sketched in Figure 1. This hopper will have an aperture of 5m2 (to suit delivery vehicles) and will act as a funnel: up to 8m3 of grain dumped in the hopper will be constrained to flow into the silo via the 200mm diameter cylindrical chute indicated. It is estimated that the maximum flow rate through this chute will be roughly 100kg/min. The measurement must therefore be made in the region shown in the figure.
Figure 1. Sketch of the silo feed hopper and required location of the grain flow monitor (not to scale).
Suggested Measurement method
One measurement method suggested is the use of a hinged impact plate, as illustrated in Figure 2. If the plate is mounted in the measurement region just below the feed hopper (Figure 1) to intercept the grain flow into the silo, there will clearly be a force generated on the plate. If the plated is supported by a spring as illustrated in Figure 2 then the angle/position of the plate will be a measure of the instantaneous grain flow rate. (And there are other methods of transducing the force due to the grain on the plate.) However there may well be other methods of grain flow measurement applicable to this situation, some of which may not involve contact with the grain as it drains from the funnel. Some of these alternative methods may be capable of providing better precision, or better serviceability and reliability.
Measurement System Specification
Because the design of the silo is not finalised, a detailed instrument specification is not available. Therefore some judgment will be required, and this situation offers some freedom in the instrument design.
However the following points must be accommodated in your design.
- Ideally the mass of grain within the silo is required to a precision of better than
±100kg.
- The type of grain will vary, and therefore so will the bulk density.
- The silo will be installed outdoors, and therefore an operating environment of at least 0?C to +50?C is expected. A significant level of dust may be expected from the general handling of dry grain.
- Output from the measurement system and simple operational control must be via a host computer. The protocol is initially proposed to be MODBUS over RS-232 (the client had previously standardised on this interface). However the cable run to the host computer may be 50m. Hence:
- estimate the data rates that will be required for the link and determine if your instrument could be interfaced to communicate adequately via MODBUS over RS232. If not state the performance of the data link required.
and
- include the outline design of the communications link in your design; or you may wish to specify a more appropriate link: if so, explain and justify this in your design.