# Expectation vs. Reality: Attitudes Towards a Socially Assistive Robot in Cardiac Rehabilitation
## 2 Background
### Robot Therapy in Cardiac Rehabilitation
#### 2.2.1 Human-Robot Sensor Interface  
The system is comprised of a sensor interface, aiming to measure all relevant variables of the therapy such as cardiopulmonary parameters (e.g., heart rate and blood pressure), spatiotemporal parameters (e.g., speed, cadence, and step length) and exertion perception scale (i.e., the Borg scale, defined as a qualitative scale to estimate exertion while performing physical activity [23]). To measure these variables a heart rate sensor (Zephyr HxM, Medtronic, USA), an IMU (MPU-6050, Invensense, USA) and a Laser Rangefinder (URG-04 LX-UG01, Hokuyo, Japan) were integrated in the interface. Finally, a Nao robot (Softbank Robotics, France) is the social agent that manages all the data provided by the sensor interface to assist the patient and provide feedback, considering the events that occur within the session.  
The architecture of the interface comprises different nodes (e.g., sensors and robot nodes) to properly handle the difference in sampling rates and the amount of information acquired by the system. In the case of the sensor interface, the output of each node is the data processed; and for the robot node is the corresponding behavior and feedback. Afterwards, a top layer of the interface architecture controls the time flow of the session (i.e., the start of the session, cooldown beginning and end of the session). Complete sensor data is stored in a database and is analyzed online to manage the robot interaction with the user. Robot's behaviors have been designed to interact with the patient while monitoring its performance, with the aim to having a positive influence on their motivation to perform the exercise (See Figure 3); and to communicate with the therapists if an event of emergency occurs during the therapy (e.g., heart rate over the maximum allowed level and dizziness).  
Figure 2: Social robotic companion in CR. **(a)** Exploration of the exercise session environment was carried out as a first stage. **(b)** The system design and performance were evaluated under laboratory conditions with a healthy user. **(c)** A pilot study was conducted with four patients under clinical conditions during the first four sessions.  
As depicted in Figure 3, the social robot based its behavior on three situations [6] (e.g., motivation, warning, and emergency, which are triggered depending on the time of the session and the data provided by the interface). Likewise, these behaviors were developed aiming to provide a similar assistance, as health professionals do. Previous observations of typical therapist-patient interactions were perform in order to develop suitable behaviors to each context. The custom-designed graphical user interface (GUI) is running on a tablet, which is available to allow the user to interact with the system, as well as to respond to the robot's requests. As it can be seen at the Figure 4, the GUI has different panels. The Control panel includes the widgets that are managed by the user (i.e., Borg Scale Buttons, Start, Stop, and Cooldown buttons), this widgets are in charge of record the time flow of the therapy and also store the Borg scale perceived by the patient through the session. Additionally, the Display panel (i.e., variables and patient displays) is developed to visualize the patients' parameters and data. This panel is useful for the clinicians as they are constantly watching over the heart rate status and the exercise parameters performed by the patients. Different behaviors require confirmation on the patient's side. Similarly, the robot asks for the Borg scale that must be delivered through the interface.  
Figure 4: Graphical user interface (GUI) for cardiac rehabilitation human–robot interface.  
Figure 3: Experimental setup of a treadmill-based therapy at the cardiac rehabilitation facility.