Pen Tip Position Research Articles

Strategies of Pen Tip Path Estimation and of Workload Comparison for Handwriting Tasks

The magnitude of impulse and work at pen tip, which are related to the fingertip force, may be indicators of fatigue and pain during writing. Previous methods used specially prepared pens for testing which have different sizes and weights from those commercially available; however, they are not suitable for evaluating the operation and workload of ordinary handwriting tasks. This article proposes a data processing method of a six-axis force-torque sensor for determining the contact state of the pen tip and calculating the position and work of the pen tip without adding anything to a commercially available pen. The proposed method consists of kinematic calculation of the pen tip position as the observation and probabilistic determination of the contact state of the pen tip. The performance of the proposed method is presented by applying to the time-series data of force vector and moment vector during handwriting tasks of symbols. The data was measured by a low-resolution high-frequency 6-DoF force-torque sensor. Multiple handwriting tasks with the same or different load at one time were set. It was confirmed statistically whether the work amount with one pen tip can be evaluated appropriately if the work amount is the same or different. The experimental results demonstrate that the proposed method can compare the movement distance and work of the pen tip, depending on the severity of the writing task.

RELATIVE POSITIONING OF STROKE-BASED CLUSTERING: A NEW APPROACH TO ONLINE HANDWRITTEN DEVANAGARI CHARACTER RECOGNITION

In this paper, we propose a new scheme for Devanagari natural handwritten character recognition. It is primarily based on spatial similarity-based stroke clustering. A feature of a stroke consists of a string of pen-tip positions and directions at every pen-tip position along the trajectory. It uses the dynamic time warping algorithm to align handwritten strokes with stored stroke templates and determine their similarity. Experiments are carried out with the help of 25 native writers and a recognition rate of approximately 95% is achieved. Our recognizer is robust to a large range of writing style and handles variation in the number of strokes, their order, shapes and sizes and similarities among classes.

Validation of digital spiral analysis as outcome parameter for clinical trials in essential tremor

Essential tremor, one of the most prevalent movement disorders, is characterized by kinetic and postural tremor affecting activities of daily living. Spiral drawing is commonly used to visually rate tremor intensity, as part of the routine clinical assessment of tremor and as a tool in clinical trials. We present a strategy to quantify tremor severity from spirals drawn on a digitizing tablet. We validate our method against a well-established visual spiral rating method and compare both methods on their capacity to capture a therapeutic effect, as defined by the change in clinical essential tremor rating scale after an ethanol challenge. Fifty-four Archimedes spirals were drawn using a digitizing tablet by nine ethanol-responsive patients with essential tremor before and at five consecutive time points after the administration of ethanol in a standardized treatment intervention. Quantitative spiral tremor severity was estimated from the velocity tremor peak amplitude after numerical derivation and Fourier transformation of pen-tip positions. In randomly ordered sets, spirals were scored by seven trained raters, using Bain and Findley's 0 to 10 rating scale. Computerized scores correlated with visual ratings (P < 0.0001). The correlation was significant at each time point before and after ethanol (P < 0.005). Quantitative ratings provided better sensitivity than visual rating to capture the effects of an ethanol challenge (P < 0.05). Using a standardized treatment approach, we were able to demonstrate that spirography time-series analysis is a valid, reliable method to document tremor intensity and a more sensitive measure for small effects than currently available visual spiral rating methods.

Right-sided spatial difficulties in ADHD demonstrated in continuous movement control

Children with Attention Deficit Hyperactivity Disorder (ADHD) often show spatial attentional deficits, exhibiting a subtle rightwards bias, possibly due to dysfunction within the right hemisphere fronto-parietal network. Approximately 50% of children with ADHD also show signs of movement dysfunction. The nature of this movement dysfunction and possible interactions with spatial attention difficulties has not been clearly described. This study compared 31 children with and 31 children without ADHD on a movement kinematic task that tested hand-drawing movement precision. Participants used an electronic pen on a digitizing tablet. The pen tip position was sampled as X and Y coordinates at 200Hz. The task was to join targets of either 10 or 20mm diameter that were separated by a distance of 62.5 or 125mm. Constant error in the X and Y planes, peak absolute velocity and acceleration, movement time, the number of pauses and pause time were analysed. Apart from a significantly increased rate of acceleration across all conditions, the children with ADHD demonstrated no temporal difficulties with the task; rather they showed subtle spatial difficulties, possibly suggestive of cerebellar involvement. The children with ADHD showed difficulties in accuracy of movement towards the right. They were less accurate in the X plane when moving towards the right-sided targets over the long distance. Greater variability in target accuracy was shown when moving towards the small target on the right side. The children with ADHD made significantly more pauses on the left target, when preparing the right movement, than the control group. These results suggest that the subtle spatial bias towards the right that has been demonstrated in ADHD in spatial attention also extends into the continuous movement domain.

A video-based text and equation editor for LaTeX

In this paper we present a video based text and equation editor for LaTeX. The system recognizes what is written onto paper and generates the LaTeX code. Text and equations are written on a regular paper using a board marker, and a USB camera attached to a computer is used to capture and record the pen-tip positions in each consecutive image frame. Characters and symbols are represented as separate finite state machines (FSMs). They are written in an isolated manner and they are recognized on-line using the FSMs. In the last step, LaTeX code corresponding to recognized characters and symbols is generated.

Cue dependent right hemineglect in schizophrenia: a kinematic analysis

OBJECTIVESSchizophrenia may result from disturbed attentional processes and/or defective internal cueing. Attention for subsequent action within a cued movement task was therefore studied, testing specific hypotheses of hemispheric dysfunction and...

Response (re-)programming in aging: a kinematic analysis.

Age-related motor slowing may reflect either motor programming deficits, poorer movement execution, or mere strategic preferences for online guidance of movement. We controlled such preferences, limiting the extent to which movements could be programmed. Twenty-four young and 24 older adults performed a line drawing task that allowed movements to be prepared in advance in one case (i.e., cue initially available indicating target location) and not in another (i.e., no cue initially available as to target location). Participants connected large or small targets illuminated by light-emitting diodes upon a graphics tablet that sampled pen tip position at 200 Hz. Older adults had a disproportionate difficulty initiating movement when prevented from programming in advance. Older adults produced slower, less efficient movements, particularly when prevented from programming under greater precision requirements. The slower movements of older adults do not simply reflect a preference for online control, as older adults have less efficient movements when forced to reprogram their movements. Age-related motor slowing kinematically resembles that seen in patients with cerebellar dysfunction.

Visual cues and the handwriting of older adults: a kinematic analysis.

Kinematic techniques determined the nature of any age-related changes in the fluency of handwriting movements and also the extent to which any changes can be related to a differential utilization of visual feedback. To quantitatively document the kinematics of handwriting movements, 24 young and 24 older adults were compared by having them write simple cursive letter ls 4 times on a graphics tablet, under 4 different visual conditions (no vision, non inking pen, inking pen, and lined paper). Pen tip position was sampled at 200 Hz, from which kinematic indexes of movement efficiency and consistency were derived. Quantitative differences in movement trajectories were found in the older adults, who produced less efficient movements with a concomitant increased utilization of external visual cues. Older adults made a differential use of visual feedback to modify movement trajectories, rather than to control the effects of neural noise. Handwriting movements of older adults resembled only to a limited extent those of patients with Parkinson's disease.

Could bradykinesia in Parkinson's disease simply be compensation?

Even normal movements can be slow and hesitant. To distinguish between bradykinesia and the simple slow inefficiency sometimes seen in normal movement, we matched the movement durations of 12 patients with Parkinson's disease (PD) and 12 age-matched controls and examined end-point accuracy, number of submovements, force inefficiency, and relative duration of acceleration and deceleration phases of movement. Subjects used an electronic pen which sampled pen-tip position at 200 Hz, and performed a sequence of drawing movements to nine targets (0.5, 1, or 2 cm diameter) upon a WACOM SD420 graphics tablet. Patients could be trained to move at the preferred speed of controls (and vice versa). When moving at the same fast speed as controls, patient's movements were less accurate (increased end-point spread). Even when moving at their own preferred speed, patients' movements were less efficient (more submovements, more zero crossings in acceleration function) than controls moving at the same speed. If bradykinesia simply reflected increased caution and visual guidance, we would expect patients to exhibit prolonged decelerative phases of movement associated with terminal guidance. However, patients consistently required prolonged accelerative phases of movement, suggesting that there was a problem in generating appropriate movement forces to produce the required end-point accuracy. It is hypothesised that bradykinesia is not simply a compensation for defective preparatory processes, but may reflect a defective internal cue in PD which disrupts and impairs the outflow of motor responses.

A Comprehensive Survey on On-line Handwriting Recognition Technology and its Real Application to the Nepalese Natural Handwriting

Handwriting Recognition Technology has been improving much under the purview of pattern recognition and image processing since a few decades. This paper focuses on the comprehensive survey on on-line handwriting recognition system along with the real application by taking Nepali natural handwriting (a real example of one of the cursive handwritings). The survey mainly includes pre-processing, feature vector and similarity measures in between the non-linear 2D sequences of coordinates, and their effective applications. A very highlighting topic "Dynamic Time Warping Algorithm'' (DTW) is introduced, which has been popular in determining the distance between two non-linear sequences ranging from handwriting to speech recognition. Besides these contemporary research issues/areas, stroke number and order free Nepalese natural handwritten recognition system is presented in the second step. Writing one's own style brings unevenness in writing units, which is the most difficult part to classify. Writing units reveal number, shape, size, order of stroke, and speed in writing. Variation in the number of strokes, their order, shapes and sizes, tilting angles and similarities among characters from one another are the important factors, which are to be considered in classification for Nepali. This paper utilizes structural properties of those alphanumeric characters, which have variable writing units. It uses a string of pen tip's positions and tangent angles of every consecutive point as a feature vector sequence of a stroke. We constructed a prototype recognizer that uses the DTW algorithm to align handwritten strokes with stored strokes' templates and determine their similarity. Separate system is trained for original and preprocessed writing samples and achieved recognition rates of 85.87% and 88.59% respectively. This introduces novel real time handwriting recognition on Nepalese alphanumeric characters, which are independent of number of strokes, as well as their order. Key Words: Handwriting Recognition System; Pre-processing; Feature Vector; Dynamic Time Warping; Agglomerating Hierarchical Clustering; Nepali. DOI: 10.3126/kuset.v5i1.2845 Kathmandu University Journal of Science, Engineering and Technology Vol.5, No.1, January 2009, pp 31-55