1.1. Indoor air pollution

According to the ^{World Health Organization (2020)}, air pollution is the world’s largest environmental health risk, accounting yearly for about 8 million deaths (4.2 million deaths from outdoor air pollution, and 3.8 deaths from indoor air pollution). According to the same source, about 90% of the world’s population breathe polluted or contaminated air.

Most of the people spend 80% to 90% of their time indoors. Therefore, IAQ has a direct impact on overall health (^{Saini et al., 2020}).

According to the United States (US) Environmental Protection Agency (EPA), IAQ is defined as the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. The sources and health effects of some common indoor pollutants such as fine Particulate Matters of diameter < 2.5 μm (PM2.5), Volatile Organic Compounds (VOCs) and other common pollutants are explained in (^{Tran et al., 2020}).

Although CO₂ is produced both naturally and through human activities, it is not classified as an air pollutant. However, it is treated as a pollutant because the amount of oxygen required for breathing becomes insufficient at high concentrations of CO₂ in an indoor space. Temperature and relative humidity also contribute to the sense of thermal comfort (^{Jo et al., 2020}).

1.2. COVID-19

As is implied in the name COVID-19, ‘CO’ stands for ‘COrona,’ ‘VI’ for ‘VIrus,’ and ‘D' for Disease, and 19 represents the year of its occurrence. The COVID-19 pandemic is considered as the most global challenge that the humankind faced since the 2^nd World War (^{Chakraborty & Maity, 2020}).

In a few short months, COVID-19 becomes global pandemic and economic disaster. As of 15 June 2021, more than 177 million people officially tested positive for the virus and about 3.84 million had died as a result (^{CoronaTracker, 2021}).

Figure 1 shows how the rate of confirmed patients, recovered patients, and deaths is increasing exponentially.

Figure 1 COVID-19 statistics. 

Home isolation for both healthy and infected individuals with mild symptoms is implemented in many countries. Isolation with improper ventilation or sterilization could lead to severe health problems. The situation could be even worse if the IAQ was poor to begin with (^{Abouleish, 2021}).

Adequate ventilation, air filtration, humidity regulation and temperature control are key strategies, which can be combined to improve indoor air quality and protect occupants from airborne viruses (^{Brittain et al., 2020}).

1.3. Monitoring of IAQ

Monitoring of parameters such as temperature, humidity, CO₂ and other air quality parameters is a major concern to businesses, educational institutions, and health organizations because it can significantly impact the health, comfort, well-being and productivity of the individuals (^{Yousuf et al., 2017}).

Pollutants that are most commonly found in indoor air environments include VOC, CO₂ and PM (^{Mancini et al., 2020}).

With the increased concern about IAQ in recent years, IAQ analyzers combining multi-sensors are available in the market and come as separate systems, it is considered costly and not easy-to-use for continuous monitoring of IAQ (^{Tahsiin et al., 2020}).

The emergence of cost-effective sensors and communication protocols provides improved living environments. Traditional approaches based on building automation and control systems consider buildings equipped with many different sensors. However, it is expensive, principally when it has to be implemented in existing buildings. It may require a complex integration process for sensors as well as maintenance and calibration processes (^{Ribino et al., 2020}).

Some common indoor air pollutants and their permissible levels, as stated in WHO and European standards are summarized in Table 1 (^{Settimo et al., 2020}).

1.4. Robotics, AIQ and COVID 19

The prime utilization of robots is to minimize person-to-person contact and to ensure cleaning, sterilization and support in indoor facilities. This will result in minimizing the life threat to personnel taking an active role in the management of the COVID-19 pandemic (^{Khan et al., 2020}).

Robots have been developed to take on dull, dirty, and dangerous jobs. Combating infectious diseases involves an environment that is unsuitable for human workers. For disease prevention, robot-controlled noncontact surface disinfection is being used because COVID-19 spreads not only from person to person but also via contaminated surfaces. Instead of manual disinfection, autonomous or remote-controlled disinfection robots could lead to cost-effective, fast, and effective disinfection. Robots could navigate high-risk areas and continually work to sterilize all high-touch surfaces (^{Yang et al., 2020}).

2.1. Materials

Mobile robot arm is a mechanical manipulator that exhibits similar functions of a human arm. It consists of three revolute joints and one prismatic wheeled joint. Revolute joints allow rotational motion about Z-axis while prismatic joint allows translation motion along X and Y directions. The last linkage at the terminal of the kinematic chain is called end-effector. A gripper is employed as the end-effectors of robot manipulator. This gripper is used for holding sprinkler plastic alcohol nozzle. Basic design of the mobile robot arm was designed in Autodesk Inventor software and further kinematic analysis is done with the help of a numerical computing environment as discussed in (^{Gaber et al., 2016}).

A simple four Degree of Freedom (DoF) mobile robot is considered for the analysis. The different DoFs are shown in Figure 2.

Figure 2 The joint motion of the three revolute joints and the prismatic joint. 

The three revolute joints are termed as θ₁, θ₂ and θ₃ whereas P denotes the prismatic joint. The workspace of the mobile robot arm can be described by the set of points that can be reached by its sprinkler, considering a physically possible mechanical configuration (^{Patel, 2016}). The constraints for each joint are given below in Table 2.

Figure 3 illustrates the fabricated mobile robot arm which includes the following:

Figure 3 Experimental system setup. 

Remotexy is mobile software for smartphones which applied to use a mobile Graphical User Interface (GUI) for Arduino Mega. The designed mobile robot needs to be capable of communicating with the mobile phone. Different communication systems can be adapted for this communication. The communication over HC06 Bluetooth module is utilized to control the three revolute servo motors and the prismatic dc motor via mobile phone.

Figure 4 shows the GUI of the mobile application applied for the control of the dc motor to make the mobile platform start at a room’s home position and for the control of the servo motors to test the manipulator’s rotational motion.

Figure 4 Mobile GUI to control the mobile robot arm. 

2.2. Methodology

Figure 5 illustrates the movement algorithm of the designed mobile robot. The movement of the mobile platform is based on the odometry method used to move the mobile robot in the x and y directions along a room while the movement of the translation and rotation of the manipulator is based on the inverse kinematics solution to get /θ1, θ2, and θ3 (^{Gaber et al., 2021}), which calculates the joint variables that would put the sprinkler in the desired position.

Figure 5 Flow chart of the mobile robot’s movement algorithm. 

The readings (outputs) of the different sensors are divided into zones as shown in Figures 6, 7. Based on the accepted range for each parameter, the appropriate zone is determined as illustrated in Table 3. The result from the processor is fed to the mobile arm robot, which then presents the message to the user on the mobile application as shown in Figure 8, which specify the action to be taken.

Figure 6 “A” zones for (T, RH & CO₂). 

Figure 7 “B” zones for (PM2.5, VOC & CO₂). 

Figure 8 Message presented to the user.