## 1 Introduction
[24] also proposed the upper limb posture and concurred with an independent study by [PERSON] et al. [28]. Both studies recommend that the patient should be sitting on a chair in a 90\({}^{\circ}\)[PERSON] Then, the patient should maintain shoulder at 0\({}^{\circ}\), elbow at 90\({}^{\circ}\), and forearm in resting position. The therapist, if necessary,  
Figure 1: Pinch test as in the UE-FMA protocol. may support the patient's elbow at 90\({}^{\circ}\)[PERSON] [PERSON] has suggested that the therapist can use a bedside table to support the patient's arm and elbow. The use of bedside table is supported by other studies, which reported that the arm weight leads to abnormal coupling between shoulder abduction and elbow flexion due to abnormal muscle co-activation required to compensate the weight of the arm [29]. Therefore, [PERSON] and colleagues used arm weight support to reduce the activation of those muscles (e.g., biceps), which otherwise would be involved in pinching [30; 31]. Recently, the research community [21; 32; 33; 34; 35; 36; 37; 38; 39] have been working on automating UE-FMA, but few of them involved the pinch grip. [PERSON] and his colleagues [40; 41] implemented a glove with built-in Force Sensing Resistor (FSR) sensors as the data [PERSON] system to measure the patient's pinch force during the evaluation process. Nevertheless, some post-stroke patients with severe to moderate impairment have muscle contracture and spasticity that lead to difficulties in wearing the glove. In later studies [42; 43], the FSR sensor was attached to the pincer object such that the patient is no longer required to wear a glove. The pinch force threshold values that distinguish between slip (score 1) and non-slip (score 2) onsets are useful in determining the baseline measurements to evaluate the effectiveness of pinch rehabilitation for both right and left hands. In both studies, the discrimination between scores 1 and 2 was based on the ability of the subject to exert pinch force up to a threshold value. However, this threshold pinch force value was selected by the therapist which may open the possibility for uncertainty. Moreover, these studies still have not addressed the issues related to subjectivity of the manual pull and the limitations of the FSR sensors used in the data acquisition system. Generally, FSR sensors (also known as a thin-film sensor) have been used for many applications [44] but they suffer from performance variation as well as low performance [45; 46]. The variation in performance is attributed to the conductive material on the sensor layers being sensitive to temperature and deformation on the surface [47]. In addition, the variation in performance can be attributed to the inability to follow the standard calibration procedures resulting in different calibration results compared to those in the manufacturer's datasheet. On the other hand, low performance can be attributed to variation in voltage gain, high hysteresis, nonlinearity, and inaccurate measurements in real-time pinching [48]. [PERSON] et al. [49] investigated the performance of the thin-film sensor when attached directly to human skin. The results show a large measurement error of 23% using the standard calibration techniques. In addition, the pressure distribution on the sensing area may not be uniform during slippage due to different pinching contact location. The main objective was to develop an automated data acquisition system for pinch assessment based on the standard UE-FMA protocol. In this study, the following research questions were addressed: (1) Does the slip onset occur at the maximum pinch force? (2) Is there any significant difference between right and left hands in pinch and pulling forces at the slip onset? In this study, the authors hypothesized that the maximum pinch force exerted by the volunteer against the automatic pulling would be located at the slip onset.