Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115, USA.
Ergonomics. 2009 Oct;52(10):1259-64. doi: 10.1080/00140130903023691.
Reaction force measurements collected during typing on keyboard trays contain inertia artefacts due to dynamic movements of the supporting work surface. To evaluate the effect of these artefacts, vertical forces and accelerations were measured while nine volunteers touch-typed on a rigid desk and a compliant keyboard tray. Two signal processing methods were evaluated: 1) low pass filtering with 20 Hz cut-off; 2) inertial force cancellation by subtracting the accelerometer signal. High frequency artefacts in the force signal, present on both surfaces, were eliminated by low pass filtering. Low frequency artefacts, present only when subjects typed on the keyboard tray, were attenuated by subtracting the accelerometer signal. Attenuation of these artefacts altered the descriptive statistics of the force signal by as much as 7%. For field measurements of typing force, reduction of low frequency artefacts should be considered for making more accurate comparisons across groups using work surfaces with different compliances. Direct measures of physical risk factors in the workplace can improve understanding of the aetiology of musculoskeletal disorders. Findings from this study characterise inertia artefacts in typing force measures and provide a method for eliminating them. These artefacts can add variability to measures, masking possible differences between subject groups.
在键盘托上打字时收集的反作用力测量值包含由于支撑工作面的动态运动引起的惯性伪影。为了评估这些伪影的影响，当九名志愿者在刚性桌子和弹性键盘托上触摸打字时，测量了垂直力和加速度。评估了两种信号处理方法：1）截止频率为 20 Hz 的低通滤波；2）通过减去加速度计信号来消除惯性力。通过低通滤波消除了两种表面都存在的力信号中的高频伪影。通过减去加速度计信号，衰减了仅在打字时出现在键盘托上的低频伪影。这些伪影的衰减通过多达 7%的改变了力信号的描述性统计数据。对于打字力的现场测量，应该考虑减少低频伪影，以便在使用具有不同顺应性的工作面的不同组之间进行更准确的比较。工作场所物理风险因素的直接测量可以提高对肌肉骨骼疾病病因的理解。本研究的结果描述了打字力测量中的惯性伪影，并提供了一种消除它们的方法。这些伪影会增加测量值的变异性，掩盖了不同实验组之间的可能差异。
