## 3 Results and Discussion  
Using the prototype pulse simulator, this study performed a series of tests and produced pulse pressure waveforms over a wide range of age groups. The performance of the simulator was then evaluated by assessing the age-specific pulse waveforms generated by it. Human radial pulse pressure waveforms are formed by complex physiological mechanisms  
Figure 3: 3D cam-based pulse pressure waveform simulator: (**a**) A conceptual block diagram of the cylindrical 3D cam-based simulator platform capable of generating age-specific pulse pressure waveforms including a 3D cam rotation control motor, an age control motor, and a diastolic pressure control motor; (**b**) the 3D cam-based simulator. of the cardiovascular system, and aging has a significant effect on the magnitude and shapes of pulse waveforms. Thus, the performance evaluation focuses on if the pulse simulator is capable of generating age-dependent pulse waveforms that can capture the physiological characteristics of pulse waveforms associated with aging. Moreover, the accuracy of pulse pressure waveforms is quantitively analyzed using mathematically obtained age-related pulse waveforms based on in vivo data. Figure 4 shows the pulse pressure waveforms generated by the pulse simulator from 15 to 85 years of age with 10-year increments by changing the position of the cam follower assembly along the 3D cam. Typically, the increase in arterial stiffness with aging results in the increment of the amplitude and pulse wave velocity of the reflected wave [25]. This leads to an increase in the magnitude of pulse waveforms and a decrease in the interval between the first and second peaks of the waveforms. These trends are observed in the experimental results. As shown in the graphs in Figure 4, the peak pressure values increase as age increases. Moreover, the distance between the first peak and other smaller peaks decreases as the age increases from 15 to 85. In fact, the results show that the magnitude of the pulse pressure, the difference between the peak pressure (systolic pressure) value and the minimum (diastolic pressure) value, is increased from about 30 mmHg to 75 mmHg with the increase in age. Note that the diastolic pressure was set to 80 mmHg in this study. Thus, the results indicate that the pulse pressure waveforms produced by the 3D cam-based pulse pressure simulator can represent realistic age-dependent pulse waveforms that are physiologically consistent with human radial artery pulse pressure (RAPP) waveforms. To further evaluate the (artificial) pulse pressure waveforms (produced by 3D CAM), they are compared with (human) approximate pulse pressure waveforms. To quantitatively analyze the pulse waveforms, two indexes are employed. First, the L\({}^{2}\) error, the best method to evaluate the error between two consecutive data through least-squares fitting, between the pulse pressure waveforms generated by the developed simul  
Figure 4: Age-specific blood pressure waveforms artificially generated in a 3D cam-based age-specific pulse pressure simulator: (**a**) a pulse pressure waveform graph of 15 years old; (**b**) 25 years old, (**c**) 35 years old; (**d**) 45 years old; (**e**) 55 years old, (**f**) 65 years old; (**g**) 75 years old; (**h**) 85 years old. human waveforms, is calculated. In addition to the error analysis, the radial Augmentation Index (AI) value is analyzed. The AI is clinically used as a measure of vascular stiffness with age, and it is expressed by the following equation. Since the small error between AI values means that the pulse pressure waveforms are generated under conditions of clinically similar vascular stiffness, it is used for clinical similarity analysis between pulse pressure waveforms. \[\text{Radial Augmentation Index }(\text{AI})=\frac{\text{Late Systolic Pulse Pressure}}{\text{Early Systolic Pulse Pressure}}\ \times\ 100\ (\%) \tag{1}\]  
Collecting pulse waveforms using human subjects of all ages is a daunting task.