Building Management and Control Systems Assignment 2018/19

BRUNEL UNIVERSITY
MSc. IN BUILDING SERVICES ENGINEERING
ME551: BUILDING MANAGEMENT AND CONTROL SYSTEMS
CONTROL SYSTEMS ASSIGNMENT 2018/19
STUDENT NAME
STUDENT ID NUMBER
INSTRUCTOR (PROFESSOR)
DATE OF SUBMISSION
12TH DECEMBER 2018
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PART 1: OPEN LOOP
1.1 Block diagram demonstrating the control signal and the radiator heat output.
1.2 Open-loop block diagram for the radiator heat output and the room temperature.
1.3 Discussion
Radiators and convectors are the key means of heat emission in most building services.
There are alternatives which may be used to transfer up to 40 percent of the heat by radiation1.
These radiators provide a local spot heating and are efficiently implemented in buildings with
high air change rates. The low pressure water panel radiator has lower energy consumption and
lower air temperatures with reduced stratification at high levels of implementation. It has a rapid
warm-up, responsive control and no air movement2. The radiator heat output is implemented to
warm the building but heating system is susceptible to effects from the environment.
1 Damian, Muniak, (2018). Role, Types and structure of the heating installation regulation valves: Types, structures,
characteristics, and applications.
2 Mehta, Paul, Desh (1980); Dynamic Thermal responses of buildings and systems; Retrospective Theses and
Dissertations; IOWA State University. https://lib.dr.iastate.edu/rtd.
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At this point, the open loop system is described using the first order system. There is no
feedback channel hence the system output may either be as intended or not3. The system is
susceptible to disturbances in the surrounding and as a result the system output is not bounded.
This is an undesirable characteristic in the system design and implementation as it may result in
errors transmitted to other systems in cascaded system design. Open loop systems do not observe
the system output and as a result, they do not find application in machine learning. These
systems depend solely on the model of the plant and its current state4. Such a system counteracts
against the environmental noises and is designed such that the disturbances are not eliminated.
The system is not unstable.
The room heater dynamic model represented in the first order follows the function,
G ( s ) = K
1+τs e−Ls
K = DC gain. It is given as the ratio of the output voltage and the input voltage.
K= y ( ∞ )
u ( ∞ )
τ =2 minutes
%% room heating using the LPHW Panel Radiator
L=0.6; %dead-time
tau=2; %Time constant
K=3; % DC Gain
s=tf('s'); %symbolic transfer function
R1=K*exp(-L*s)/(tau*s+1) % G(s)
3 Stanford Research Institute (2005). Patterns of Energy consumption in the United States. Prepared for the office of
science and Technology, Washington, DC. Stanford, Ca. Stanford Research Institute.
4 Hamilton, D.C.; Leonard, R.G; and Pearson, T.; “Dynamic response characteristics of a Discharge air temperature
Control system at near full and part heating load. “ ASHRAE Trans. 80 (p.181).
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The DC gain of the open loop system is given as 3
Assumptions
(i) The noise is a constant value; zero-mean additive white Gaussian noise is introduced
in the system as the source of the system disturbance.
(ii) The room temperature reader is well calibrated depending on the ambient temperature
of the room.
(iii) The room temperature is not disrupted by air flow from the ventilation sections of the
room such as the windows, louvers, and other ventilation spaces.
PART 2: CLOSED LOOP
Adding a proportional feedback controller to the heating system as a controller improves
the control and system response. The proportional gain controller is adjusted to provide different
response. The gain parameter reduces the steady state error in the system response though when
it exceeds a given value, the output oscillates and may cause system instability. Based on the
information provided, the response of the heater in the LPHW heater, the time constant is small
enough to render the response instantaneous. The proportional controller decreases the rise time,
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