# Medical Robotic Bed to Prevent Pressure Sores
## 1 Introduction  
A significant number of people are receiving long-term care in hospitals and at home for various conditions, including dementia, disability, and other diseases. Caring for such patients requires nurses to possess specialized skills and qualifications in addition to requiring them to perform many simple and labor-intensive tasks. Therefore, patient care is considered a suitable field for the application of robots and artificial intelligence. Patients with severe conditions who need nursing care spend most of their time in bed. Accordingly, several researchers have conducted studies to robotize a bed for such patients. A few researchers have proposed a bed with a robotic arm that can serve patients. [PERSON] proposed a robotic system that consists of a bed and a mobile manipulator to provide bedside assistance [1]. [PERSON] et al. presented a robotic bed equipped with two robot arms and an array of pressure sensors attached onto the matreress. They used the pressure distribution on the matreress to estimate the pose of the patient [2]. Studies on beds that control the patient's posture and sleep quality by measuring the patient's vital signals have been conducted as well. [PERSON] developed a bed with a multi-sensor matreress pad to detect heart rate, breathing rate, and body orientation [3]. In addition to these studies, a bed that facilitates the lateral rotation or transfer of immobilized patients [4] and a chair bed system [5] have been proposed. Patients who stay in bed for long periods may develop pressure sores. A pressure score occurs due to ischemia of the skin and muscles because blood circulation is impaired in parts of the body that are constantly pressed upon. Pressure sores are usually formed in areas of the skin that touch the bed when a person has been bedridden for a long time, and the incidence of pressure sores among patients in intensive care units in Korean hospitals was reported to be 38.3% [6]. Pressure sores cause multiple complications, prolong hospitalization, and increase a patient's risk of death [7; 8; 9]. When pressure abovea threshold value is applied for more than a certain amount of time, pressure sores are formed. The pressure value at which pressure sores develop varies, but in general, many researchers agree that the threshold is 32 mmHg [10]. To prevent pressure sores, various studies and expert analyses have been conducted, and a number of devices have been developed. These devices can be classified into active devices that control body pressure manually or automatically and passive devices that only relieve body pressure but do not control it. Furthermore, these devices can be classified based on whether they use body pressure information or do not use body pressure information. The most commonly used commercial product is a passive bubble air mattress that is installed on the bed. Sorbed Co. launched an active bed with an integrated pressure sore mattress and a pneumatic pump. The basic concept of this product is similar to that considered in this study, and it controls body pressure by using pneumatic actuators, but it does not use pressure information and is affected by noise issues because of the pneumatic pump [11]. Wellsense, Inc., released the Monitor Alert Protect system, which analyzes body pressure data gathered using sensors embedded in the bed mattress and sounds an alarm when there is a risk of pressure sore formation [12]. Through project INSYDE, the Fraunhofer Institute developed technology to reduce a user's body pressure by changing the posture of the bed based on measurements of body pressure distribution [13]. [PERSON] proposed a bed equipped with multiple air bladders in which the postures are controlled by motors and lead screws to prevent the formation of pressure sores. This bed utilizes body pressure distribution information, but it is impractical because it requires a large number of actuators for bed operation [14].