Kok Mun Ng

A Review on the Applications of Petri Nets in Modeling, Analysis, and Control of Urban Traffic

Urban traffic systems that possess system states that are distributed, parallel, deterministic, stochastic, discrete, and continuous are well suited for a Petri net (PN) approach. The literature survey conducted in this paper shows the vast applications of PNs in modeling and simulation, analyzing and evaluating performances, intelligent control and optimization, and congestion management in urban traffic systems. This paper outlines the related works conducted using PNs and discusses its viability, such as its contributions and limitations. Extendibility and future research potential to further the successful applications of PNs in traffic systems are discussed and proposed in this paper.

Hybrid-Actuated Finger Prosthesis with Tactile Sensing

Finger prostheses are devices developed to emulate the functionality of natural human fingers. On top of their aesthetic appearance in terms of shape, size and colour, such biomimetic devices require a high level of dexterity. They must be capable of gripping an object, and even manipulating it in the hand. This paper presents a biomimetic robotic finger actuated by a hybrid mechanism and integrated with a tactile sensor. The hybrid actuation mechanism comprises a DC micromotor and a Shape Memory Alloy (SMA) wire. A customized test rig has been developed to measure the force and stroke produced by the SMA wire. In parallel with the actuator development, experimental investigations have been conducted on Quantum Tunnelling Composite (QTC) and Pressure Conductive Rubber (PCR) towards the development of a tactile sensor for the finger. The viability of using these materials for tactile sensing has been determined. Such a hybrid actuation approach aided with tactile sensing capability enables a finger design as an integral part of a prosthetic hand for applications up to the transradial amputation level.

An Integrated Approach for Platoon-based Simulation and Its Feasibility Assessment

Research on developing mathematical and simulative models to evaluate performance of signalized arterials is still ongoing. In this paper, an integrated model (IM) based on Rakha vehicle dynamics and LWR model is proposed. The IM which imitates actuated performance measurement in signalized arterials is described using continuous timed Petri net with variable speeds (VCPN). This enables systematic discretized description of platoon movement from an upstream signalized intersection towards a downstream signalized intersection. The integration is based on the notion that speed and travel time characteristics in a link can be provided using Rakha model. This will assist the LWR to estimate arrival profiles of vehicles at downstream intersection. One immediate benefit of the model is that platoon arrival profile obtained from the IM can be directly manipulated to estimate queues and delays at the target intersection using input-output analysis without considering the effect of shockwaves. This is less tedious as compared to analysing the LWR model through tracing trajectory of shockwave. Besides, time parameters of a platoon could be estimated for self-scheduling control approach from a cycle to cycle basis. The proposed IM is applied to a test intersection where simulated queues and average delays from the IM are compared with the platoon dispersion model (PDM) implemented in TRANSYT, cell transmission model (CTM) and HCM2000 for both under-saturated and oversaturated situations. The comparisons yielded acceptable and reasonable results, thus ascertained the feasibility and validity of the model.

Platoon interactions and real-world traffic simulation and validation based on the LWR-IM

Platoon based traffic flow models form the underlying theoretical framework in traffic simulation tools. They are essentially important in facilitating efficient performance calculation and evaluation in urban traffic networks. For this purpose, a new platoon-based macroscopic model called the LWR-IM has been developed in [1]. Preliminary analytical validation conducted previously has proven the feasibility of the model. In this paper, the LWR-IM is further enhanced with algorithms that describe platoon interactions in urban arterials. The LWR-IM and the proposed platoon interaction algorithms are implemented in the real-world class I and class II urban arterials. Another purpose of the work is to perform quantitative validation to investigate the validity and ability of the LWR-IM and its underlying algorithms to describe platoon interactions and simulate performance indices that closely resemble the real traffic situations. The quantitative validation of the LWR-IM is achieved by performing a two-sampled t-test on queues simulated by the LWR-IM and real queues observed at these real-world locations. The results reveal insignificant differences of simulated queues with real queues where the p-values produced concluded that the null hypothesis cannot be rejected. Thus, the quantitative validation further proved the validity of the LWR-IM and the embedded platoon interactions algorithm for the intended purpose.

Application and validation of the LWR-IM traffic model in class II urban arterial

This paper presents investigation on the applicability and validity of the Lighthill-Witham-Richards - Integrated Model (LWR-IM) traffic model in modelling and simulating platoon progression and performance indices of traffics in urban arterials. For this purpose, the LWR-IM is applied to a class II urban arterial in the city of Klang, Malaysia. Real traffic demands are fed into the model to simulate the queuing conditions along the arterial. Simulated queues are compared with real queues observed using the two-sampled t-test and the mean absolute error (MAE). The comparison reveals low MAEs and insignificant differences of simulated queues with real queues where the p-values produced concluded that the null hypothesis cannot be rejected. Thus, this further proved the applicability and the validity of the LWR-IM.

A comparative study of the LWR-IM traffic model and shockwave analysis

A new traffic model called LWR-IM has been developed to simulate traffic dynamics in urban arterial network. The arrival profile produced by the LWR-IM could be analyzed using input-output method which is less tedious compared to analyzing the LWR using Shockwave analysis. This paper presents a comparative study of queues produced by the LWR-IM and Shockwave analysis respectively. The study reveals that the queues simulated using the LWR-IM is compatible with Shockwave analysis. More importantly, the LWR-IM provides a more efficient method to analyze the LWR, thus further ascertaining the feasibility and efficiency of the model.

Decision rules for allophone synthesis of Malay text-to-speech system

This paper presents a method for Malay text-to-speech synthesis using allophone synthesis technique. In this work, allophone synthesis is implemented with a set of decision rules which are developed to analyze the phonemes of Malay text and assists in selecting appropriate allophones for speech synthesis in the SPO256 speech narrator processor. The decision rules are found to be reliable when tested with 15 samples of Malay words. Speech of good clarity and pleasant pronunciation is successfully synthesized.