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Assessing the Effectiveness of Fuzzy-PID Controller under Temperature Setpoint Changes During Coffee Roasting Process
Abstract
Roasting coffee is an essential step in the production of coffee because it affects the flavour, aroma, and overall quality of the final product. Temperature control during the roasting process is essential to achieve a consistent and desired taste. This study seeks to assess the performance of a Fuzzy PID (FPID) controller during coffee roasting when the temperature setpoint varies. The temperature range in this study is from 34-200℃. The study employs an SR500 coffee roaster as the process plant, a FOPDT model structure, a PID-AMIGO benchmark controller, FPID-3 and FPID-5 controllers as the proposed controller. The study includes both simulation and real-time testing for the FPID-5 controller. The results for the FPID-5 controller indicated that the overshoot was reduced to 0.24% and 4.04% in simulation and 2.9% and 8.6% in real-time testing, representing an improvement of more than 90% in overshoot reduction compared to the PID controller. Thus, the proposed FPID-5 controller has been proven to effectively suppress overshoot during temperature setpoint changes in the coffee roasting process. Keywords— Arduino, FOPDT, Process control, temperature controller, real-time control.
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Due to its chemical compounds, coffee has a good taste, pleasant aroma, stimulant effect, and health benefits. Roasting is a critical process to develop a good flavor and cup quality of the coffee brew. This article reviews the coffee chemical reaction proceeds during roasting, evaluates the roasted degree by physic and chemical approach and biochemical changes. The articles were compiled from ScienceDirect, SpringerLink, ResearchGate, and Google Scholar. Out of all of the collected papers, 40 articles were covered in this paper. The initial process of roasting is water content evaporating and continuously is followed by roasting phase including pyrolysis, Maillard reaction and caramelization. The roasted coffee degree is determined by visual, weight loss, acidity, and pop beans sound. The bioactive compounds of coffee such as chlorogenic acids, caffeine, and trigonelline affect brewed coffee’s cup quality. Chlorogenic acid and trigonelline significantly decrease during the roasting process. However, caffein is quite stable during roasting. The roasted coffee performs a function in the consumers’ health since in vitro and in vivo analysis present that bronze roasted espresso has the most powerful activity as anti-inflammatory and antioxidant.
Purpose of Review
Coffee is a very popular drink and an estimated 2.25 billion cups worldwide are consumed daily. Such popularity of coffee makes it the most consumed drink next to water. Numerous studies have shown a beneficial effect of habitual and moderate coffee consumption on the functioning of the nervous, digestive, and cardiovascular systems, as well as on kidney function. Taking into account the very high prevalence of arterial hypertension in the world (31.1% of adults), much controversy has been raised about the influence of coffee consumption on blood pressure and the risk of arterial hypertension. Moreover, there have been extensive discussions about the safety of coffee consumption for hypertensive persons.
Recent Findings
There are over 1000 chemical compounds in coffee. The best characterized of these are caffeine, chlorogenic acid, trigonelline, kahweol, cafestol, ferulic acid, and melanoidins. These compounds have bidirectional influences on blood pressure regulation. The results of numerous studies and meta-analyses indicate that moderate and habitual coffee consumption does not increase and may even reduce the risk of developing arterial hypertension. Conversely, occasional coffee consumption has hypertensinogenic effects. Moderate habitual coffee consumption in hypertensive persons does not appear to increase the risk of uncontrolled blood pressure and may even reduce the risk of death from any cause.
Summary
Moderate and habitual consumption of coffee (1-–3 cups / day) does not adversely affect blood pressure in most people, including those with arterial hypertension.
The specialty coffee industry is growing and, as a result, there is an accelerated interest in modulating roast profiles to present customers with new and diverse sensory experiences. The present study investigates the chemical and sensory effects of subtle variations in the ‘development time’ phase of the coffee roasting process. Four roast profiles were studied through sensory descriptive analysis (DA), gas chromatography–mass spectrometry (GC–MS), and nuclear magnetic resonance (NMR). Multivariate analysis showed clear separation of DA, GC–MS, and NMR data. A prolonged development time facilitated a statistically significant shift in the chemical and sensory profile of the coffee. The findings suggest that a short development time increases the fruity, sweet and acidic characteristics of the coffee, whereas a longer development time shifts the balance towards a more roasty, nutty, and bitter profile. The results provide evidence that supports the effect of subtle roast profile modulations. This lays a strong foundation for the inclusion of development time as a critical control parameter in the certification system of the Specialty Coffee Association, quality control, and product development strategies.
A fuzzy self-tuning Proportional-Integral-Derivative (PID) controller, the f-SmartPID, was designed to promote high quality and stable control, and to save time and energy by ensuring continuity in nonlinear chemical processes. Because PID controllers were developed using linear structures, its performance is severely affected when working with nonlinearities of the process. A PID fuzzy filter was designed to deal with nonlinearities. Two fuzzy inference systems were incorporated to the conventional PID controller to modify the closed loop time constant when required, originating a fuzzy closed loop time constant. The f-SmartPID updates the controller gain to avoid undesirable oscillations and maintain stability in the control loop under extreme conditions. This controller was tested in a highly nonlinear process facing disturbances and set point changes, showing optimal performance in linear and nonlinear conditions. It was compared with the Conventional PID controller and the IMC (Internal Model Controller).
This research investigates the relative importance of two roasting parameters—colour (i.e., roast degree) and time—on the sensory properties of coffee. The paper draws on data from eight studies conducted using sensory descriptive analysis with trained (in six studies) or semi-trained (in two studies) assessors, focusing on a common set of attributes. The results indicated that, while both parameters significantly affected coffee flavour, colour was the stronger predictor of the two. The effects direction for both colour and time were similar and related to the rate of non-enzymatic browning, with darker roasts/longer roasting times associated with an increase in bitterness and a decrease in acidity, fruitiness, and sweetness. With respect to roasting time, we distinguished two phases, “time to first crack”, corresponding to the time between the onset of roasting and the moment where the accumulated steam pressure causes the beans to crack, and “development time”, corresponding to the time elapsed from the first crack to the end of the roasting process. The results clearly indicated that, under the same colour, time variation also influenced flavour, and in particular, development time, rather than time to first crack, had the largest effect on coffee flavour.
Coffee has been identified as a crop that has the potential to generate foreign earning for local investors but the cost of imported roasting machine is very high thus making it unaffordable for interested agripreneurs. This project detailed the development of coffee roaster using locally available materials thus reducing the cost of processing as well as achieving optimum quality. The roasting capacity of the roaster is 25kg. The roaster consists of a roasting
drum, paddles on a speed reduction gear powered by electric motor, frame, cooling fan and cooling unit with control board unit. The roaster attained a temperature of 200o, 250o and 300oC in 5, 7 and 10 minutes respectively.
On this work, the experimental implementation of a cascade control algorithm to regulate coffee roasting degree in a batch spouted bed process is presented. The control algorithm is composed of an inner control loop that regulates the temperature of the hot air inflow used to roast coffee grains inside a spouted bed, while an outer control loop, based on imaging processing techniques, tracks on real time the coffee roasting degree and decides if the inflow air temperature must be modified. To achieve this goal, a colour-matching algorithm is used to compare a colour spectrum obtained from images acquired on real time, from a peephole on the spouted bed, with the colour spectrums of several reference images with different degrees of roasting. Match scores are computed based on the similarity between the colour spectrums. With the match scores, a roasting index is finally calculated to assess the degree of roasting, allowing to automatically track the roasting progress to decide if the batch roasting process has achieved the desired roasting degree. The experimental results show that the control scheme is able to robustly achieve the desired roasting degree with excellent effectiveness.
The aim of this research is to control the temperature of roasting process to be stable. The temperature controller is needed in process of coffee roasting because of high and low temperature is very influential on the process. This paper presents the development of the coffee roaster machine where the temperature is controlled using fuzzy logic control algorithm. The temperature is sensed using PT100. The fuzzy control algorithm computes the controller output based on error and the rate of error. The fuzzy control algorithm is implemented using MATLAB. A PLC Omron is used and interfaced with PC Desktop, so that a real-time control can be conducted. A HMI is used so that a roaster machine operator can easily operates the machine. A complete PLC system and mechanical design are discussed in this paper. Experiments were conducted to verify the performance of the controller. From the experiment results, the desired temperature can be controlled with relatively small error, 0.52%. It can cause the temperature of the process relatively stable.
The effects of time and temperature on change in bean colour and kinetics of coffee roasting covering pre-roasting and over-roasting condition were investigated. Arabica coffee beans (Colombia Excelso) were dried or roasted in an oven at constant temperatures (140, 180, 200, 220, 260, and 300 °C) to obtain the profiles of mass loss and colour change. Changes in roasting rate from the first stage (high rate) to the second (low rate) were found to occur at different levels of roast loss for different roasting temperatures. Roasting curves were obtained by normalising the data of mass reductions, which comprised solid and moisture, to the initial solid mass. Changes in bean colour were found to follow a certain path regardless of the roasting temperature, as shown by the characteristic colouring curve, and were less affected by the temperature compared to the roast loss. A method of predicting the bean colour during roasting was also presented by analysing the relationships among the L*, a* and b* values.
Roasting of green coffee beans is a key step in the coffee value chain where important physical and chemical changes lead to the development of the characteristic roasted coffee flavor. The coffee's intrinsic quality is predetermined in the green bean by its precursor composition for the roaster to unlock the full potential by applying appropriate roasting conditions at temperatures above 200°C giving rise to the well-appreciated coffee aroma and taste. The knowledge of flavor precursors and the formation mechanism and kinetics of the key flavor compounds is essential for delivering a high quality cup of coffee with desirable sensory attributes through careful selection of the raw material and an improved molecular understanding of roasting technology. Coffee roasting chemistry is contributing to decoding flavor generation by describing changes in molecular composition and transformations.
Roasting is the most important step in the coffee processing. The impact of superheated
steam roasting temperature (150, 200, 250°C) and time (10-50 min) on the color (L*,
a*, b*, browning index), moisture and hardness attributes of Coffea canephora (Robusta
coffee) beans were studied. Increases in roasting temperature and time caused a decrease
in all the responses except for browning index, a* and b* values of roasted coffee beans.
A decrease in the hardness of coffee bean during roasting has been correlated to the loss
of moisture content. Coffee beans exhibit greater bean volume, pore volume and larger
micropores during roasting process, which indirectly lead to the loss of moisture content.
With regards to the prolonged superheated steam roasting, it significantly affects colour
attributes and moisture content. As the roasting temperature increased up to 250ºC, colour
attributes such as browning index, a* and b* values decreased significantly whereas
moisture content increased slightly.
Roasting is the key unit operation in converting green beans into flavorful roasted coffee. It is the roasting process during which complex chemical reactions develop the desired flavor. It also determines the physical changes in the bean microstructure. Nothing but the best roasting conditions will unfold the full intrinsic potential of the green bean and create delightful flavor sensations in the cup. This chapter will elucidate the fundamentals of the roasting process and the basic process parameters that influence the quality of the roasted coffee beans. It will illustrate how chemical reactions, dehydration, and physical changes are interlinked and how the bean time temperature master curve can influence these developments. Whether in industrial or small-scale operations, it will always need the skills of an experienced roast master for composing the ultimate blend and optimizing the roasting parameters in the first place to get the best out of the bean. This is why roasting remains an art.
Parameter self-setting fuzzy PID control algorithm for control drying temperature is applied to improve the problem about big fluctuations in temperature and high pellet broken rate of traditional control on Cold pressure ball drying system, and the controller create a intelligence temperature control system through combine fuzzy control and PID control. We can know that the control system has advantages of short adjustment time and good stable performance. It can get better performance of the dynamic response by using fuzzy PID controller than the traditional PID controller or fuzzy controller through the comparison MATLAB with the traditional PID controller and fuzzy controller.
It is well-known that PID controllers show poor control performances for an integrating process and a large time delay process. Moreover, it cannot incorporate ramp-type set-point change or slow disturbance. We discuss the above-mentioned limitations of the PID controller. Through the analysis of the limitations, simple techniques are developed to avoid these poor control performances and incapabilities. We introduce a control structure composed of two PID controllers to manipulate both the set-point change process and the input disturbance rejection process. A simple feedforward and feedback loop are proposed to treat a ramp-type set point and disturbance (low-frequency set point and disturbance). In addition, an internal feedback loop is introduced to incorporate integrating processes, and a tuning strategy using the model reduction is proposed to efficiently tune the controller for high-order processes. A dead-time compensator is used to manipulate a large time delay process more efficiently.
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