Table 4 Summary of the popular technologies used in objective pendulum test, and their advantages and shortcomings
Technology | Advantage | Disadvantage |
|---|---|---|
Potentiometer (angle) | Simple, low cost and suitable for online computer analysis [38] | Higher errors; lower stability; difficult to attach & hindering knee-joint motion [30] |
Need for differentiation to get angular velocity / acceleration [57] | ||
Goniometer (angle) | Easy to attach [57] | Questionable reliability, cause of high individual errors [58] |
Errors of joint repositioning [59] | ||
Electro-goniometer (angle) | High reliability [57] | Large non-linearity and hysteresis [57] |
Accelerometer (linear acceleration) | Stable and easy to attach. high sensitivity and excellent reliability of the pendulum test [43] less expensive; not restricting the movement [57] | Less accurate angle estimation during movement [59] |
Gyro (angular velocity) | No need for numerical differentiation; sufficient accuracy; low susceptibility to effects from the motion of the knee joint axis; no restriction of the knee joint when worn; simple and stable attached; and ability to obtain waveforms of angle, angular velocity, and angular acceleration simply and with high accuracy [57] | Stability and reliability remain problematic [57] |
Inertial Motion Units (IMUs, acceleration plus angular velocity) | Simple use | Issues concerning the validity and reliability of the measurements |
Camera-based methods | Simple use | Difficult video analysis |