Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 35 | Smart Patient Bed for Pressure-Injury Prevention |
Rayan Soltana Tyler Marrazzo |
Denghan Xiong | ||
| **Team Members: ** - Rayan Soltana (soltana2) - Tyler Marrazzo (tyleram3) - N/A () ## PROBLEM Bedridden patients can often remain in the same position for long periods of time, which could lead to sustained pressure on parts of the body. Nurses and caregivers have to periodically reposition and monitor these patients, and it's difficult to keep track and continuously know how long some areas have experienced pressure. ## SOLUTION My proposed solution is to create low-cost sensing layer/pad that sits underneath a patient and continuously measures their pressure distribution and position. Inside this pad we plan to have an array of pressure sensors connected together in a grid. We will limit the amount of of sensors to limit any ghost current, which comes from the overlap of the circuitry. This array gets fed into MUXs and then to an external ADC as we will probably need more specific values from the sensors. The digital values will the be fed into an MCU, which will processes the sensor array to determine whether pressure has remained concentrated in a region for too long and alerts the caregiver via bluetooth when the patient should be moved. **MAIN COMPONENTS** **_SUBSYTEM 1: SENSORS_** The pressure sensor subsystem provides the physical interface between the patient and the monitoring electronics. The pad will contain multiple pressure-sensitive regions distributed across its surface. Low-cost piezoresistive materials and conductive fabric will be investigated as possible methods of constructing a flexible sensor array. When pressure is applied to a sensing element, its electrical resistance changes. This change can be converted into a measurable voltage and used to estimate the relative pressure being applied to that area. The exact number and arrangement of sensors will be determined experimentally. An initial design may contain approximately 24 to 32 sensing regions, providing enough spatial information to distinguish major changes in body position without unnecessarily increasing the complexity of the sensing circuitry to limit ghost current. **_SUBSYSTEM 2 ANALOG ACQUISITION:_** The analog acquisition subsystem acts as the interface between the pressure-sensitive pad and the MCU. Because the sensors are resistive devices, voltage-divider or similar signal-conditioning circuits will convert resistance changes into analog voltages that can be measured by an ADC. Rather than dedicating an ADC channel to every pressure sensor, analog multiplexers will sequentially connect individual sensing channels to the measurement circuitry. The MCU will control the multiplexer address lines, select a sensor, allow the analog signal to settle, record its ADC measurement, and then proceed to the next sensor. This process will repeat continuously to construct a complete pressure map. The initial design will investigate using the ESP32-S3's internal ADC. If testing demonstrates that additional resolution, stability, or noise performance is required, an external ADC may be incorporated into the design. **_SUBSYSTEM 3: MCU_** The MCU subsystem serves as the primary controller and decision-making component of the system. An ESP32-S3 is currently planned because it provides sufficient processing capability, ADC functionality, GPIO resources, and integrated Bluetooth Low Energy support. The MCU will control the analog multiplexers and periodically scan the complete sensor array. The resulting measurements will be stored as a two-dimensional representation of pressure across the sensing pad. Before making decisions from these measurements, the MCU will perform calibration and filtering to reduce noise and compensate for differences between individual sensing elements. The processed measurements can then be used to identify regions experiencing elevated pressure and determine whether the overall pressure distribution has changed significantly. The system will maintain information about pressure over time rather than making decisions from a single measurement. If elevated pressure remains concentrated in a particular region while the overall pressure distribution indicates that the patient has not meaningfully repositioned, the MCU can transition the system from a normal state to a warning or alarm state. The alarm algorithm will be developed and evaluated experimentally. Important parameters may include pressure thresholds, duration thresholds, the magnitude of pressure-map changes required to classify a movement as a meaningful repositioning, and methods of rejecting brief movements or sensor noise. The MCU will perform this processing locally so that the monitoring system does not depend on an external computer or wireless connection to determine when an alarm should occur. **_SUBSYSTEM 4: BLUETOOTH / ALARM_** The communication subsystem will use Bluetooth Low Energy to transmit patient status information from the monitoring pad to a separate caregiver-facing device. BLE is integrated into the planned ESP32-S3, reducing the need for a separate wireless communication module. Rather than transmitting all raw sensor measurements, the MCU will perform the primary processing locally and transmit the resulting system state. For example, the system may communicate states such as normal operation, repositioning recommended, repositioning required, or a possible bed-exit condition if that stretch goal is implemented. The system will also include a local alarm, such as a buzzer and visual status indicator, controlled directly by the MCU. This ensures that an alarm can still be generated if Bluetooth communication is unavailable. **CRITERIA FOR SUCCESS** - Reliably acquire pressure measurements from all sensing regions without requiring a dedicated MCU input for every sensor. - Detect and display meaningful differences in pressure distribution when a user changes position on the pad. - Correctly distinguish meaningful repositioning from small movements and normal sensor variation under defined test conditions. - Continuously monitor pressure measurements and track how long elevated pressure persists in different sensing regions. - Generate a local warning or alarm when the defined prolonged-pressure condition is reached. - Successfully transmit the system's status or alarm condition using Bluetooth Low Energy. - Demonstrate reliable operation of the complete system during repeated simulated patient-monitoring tests. |
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