Serpentine tracked robots -i. e., articulated multi-tracked vehicles -are designed to move on rough terrains and used for a variety of purposes, including search and rescue operations, planetary exploration and environmental investigations. The steerability of such vehicles depends on its posture and interaction between the vehicle and the ground. In previous research, kinematic models with slip information were derived for articulated multi-tracked vehicles. Such kinematic models, however, do not allow for the slippage of the vehicle that occurs when moving at a high speed or on a slippery surface. In this paper, we derive a dynamic model on which the frictional force is acting between the track shoes of each track of the vehicle and the ground for the slippery conditions. The frictional model neglecting static friction is given by a formula for the friction coefficient function proposed in the field of Teramechanics in order to mainly analyze slip behavior. The model is also used to analyze the steering properties, or steerability of the vehicles.

In the past decade, search robots in rescue operations have been focused on and developed for the purpose of finding survivors trapped in the rubble of collapsed buildings. Most of them adopt serpentine mechanisms: they comprise of track-equipped segments that are connected by joints to obtain greater mobility in extremely complex environments. However, they might gather to catch debris between tracks or become stuck due to the mechanisms, in addition, increasing the number of segments would result in gaining weight and complicated mechanism and control system. In this paper, a new mobile mechanism: flexible mono-tread mobile track is proposed and a prototype ldquoRescue mobile track No.2 (RT-02) WORMYrdquo is developed. The vehicle is composed of a ldquoflexible chainrdquo and a spine-like structure. It is examined on mobility performance in irregular environments.

The authors present and evaluate a technique for synchronizing the internal states of a code-excited-linear-prediction (CELP) encoder and decoder after the occurrence of frame erasure. The designed technique, called ldquoduplicated transmission (DT),rdquo uses some redundant information for realizing synchronization. The encoder performs encoding processes twice and sends two codes for each frame. One code is encoded by an encoder that is initialized. The code is used in cases where the previous frame is erased. An onset detector is combined with the DT technique to select the frames to which the DT should be applied. Subjective test results suggest that, by introducing DT selectively, the number of DT frames is reducible by about 80% without degrading the subjective quality. Results demonstrate that synchronization of the internal states is effective in cases of erasure of onset. The DT technique requires no additional algorithmic delay. For that reason, it would a better choice for particular applications for which the delay has a significant impact.

This paper describes the scalable coder - G.729.1 - which has been recently standardized by ITU-T for wideband telephony and voice over IP (VoIP) applications. G.729.1 can operate at 12 different bit rates from 32 down to 8 kbit/s with wideband quality starting at 14 kbit/s. This coder is a bitstream interoperable extension of ITU-T G.729 based on three embedded stages: narrowband cascaded CELP coding at 8 and 12 kbit/s, time-domain bandwidth extension (TDBWE) at 14 kbit/s, and split-band MDCT coding with spherical vector quantization (VQ) and pre-echo reduction from 16 to 32 kbit/s. Side information - consisting of signal class, phase, and energy - is transmitted at 12, 14 and 16 kbit/s to improve the resilience and recovery of the decoder in case of frame erasures. The quality, delay, and complexity of G.729.1 are summarized based on ITU-T results.

Many omnidirectional vision sensors based on convex mirrors have been proposed for observing a 360 degrees field of view. Some have a single viewpoint using a hyperboloidal or parabolic mirror, others have a constant resolution property. Until now, there have not been any that have had both these properties. In this paper, we propose an omnidirectional vision sensor that has both properties; that is, a single viewpoint and a constant resolution. The proposed omnidirectional sensor uses two mirrors, which improves the degree of freedom of the design for satisfying each property. We discuss optimization of the design in terms of geometry and optics.

Many omnidirectional vision sensors using a convex mirror have been proposed for observing a 360 degrees field of view. Some of them have a single viewpoint using a hyperboloidal or parabolic mirror, some of the others have a constant resolution property. Until now, there have not been any that have had both these properties. In this paper, we propose an omnidirectional vision sensor that has both a single viewpoint and a constant resolution. The proposed omnidirectional sensor uses two mirrors, which improves the degree of freedom of the design for satisfying each property. We introduce three practical settings of constant resolution; angular constant, horizontal constant and vertical constant resolutions

Predictive vector quantization (PVQ) for a bandwidth scalable LSP (line spectrum pairs) quantizer was studied. In the quantizer, LSP parameters obtained from a wide-band (16-kHz sampling) speech signal were quantized using LSP parameters encoded in a narrow-band (8-kHz sampling) layer. We designed several configurations of 16-bit quantizer utilizing PVQ and compared their performance. Simulation results showed that effective exploitation of interframe and intra-frame prediction improved objective performance. Compared with a baseline algorithm, PVQ using normal inter-frame prediction achieved better SD (spectral distortion) performance by 0.15 dB, and further improvement of 0.05 dB was gained by introducing novel interframe and intra-frame prediction. Robustness against frame erasure was considered by adopting switched prediction and "forgetting" capability. The designed memory-based PVQ algorithms were found to be robust up to 20% frame erasure rate.

We propose an energy extrapolation-based concealment algorithm for an excitation signal of a CELP decoder. In the concealment algorithm, adaptive codebook excitation is generated to maintain continuity of excitation energy on consecutive frames, and high-frequency regions are replaced with random excitation processed through a high-pass filter. The cut-off frequency of the filter is switched according to mode information. The algorithm was implemented on the 3GPP AMR standard decoder, and its performance was compared with that of the standard algorithm. Listening test results suggested that improved subjective quality was produced by the new algorithm.

The paper presents an efficient spectrum coding method for super-wideband (beyond 7 kHz, e.g. 10 kHz or 15 kHz bandwidth) speech signals based on a bandwidth expansion technique. By using a 7 kHz bandwidth speech signal, its frequency band over 7 kHz is generated by the expansion technique without violating the harmonics structure of the speech signal. The bandwidth expansion is performed by pitch filtering in a frequency domain. A 7 kHz bandwidth spectrum is used as a pitch filter state, and pitch filtering is performed toward a frequency band over 7 kHz. We adopted this pitch filtering based spectrum coding (PFSC) to our proposing 7/10/15 kHz bandwidth scalable coder. The scalable coder consists of an existing standard wideband coder as a base-layer and two PFSC coders as an enhancement-layer. One PFSC coder encodes a 7-10 kHz band spectrum at 4.4 kbit/s and the other a 10-15 kHz band spectrum at 2.2 kbit/s. When the AMR-WB coder at 15.85 kbit/s is used as the base-layer, the total bitrate of the scalable coder is 22.45 kbit/s and the total algorithmic delay is 30 ms. We conducted degradation category rating (DCR) tests for both 10 kHz and 15 kHz bandwidth signals. The results show that the DMOS score of the proposed coder is better than that of the 7 kHz bandwidth original signals in both bandwidth clean speech conditions. In addition, when G.722 at 56 kbit/s is used as the base-layer instead of the AMR-WB coder, the DMOS score of this scalable coder is close to that of the 7 kHz bandwidth original signals in both bandwidth audio conditions.

A new design concept of manipulator is proposed, which is called the torque-unit manipulator (TUM). Each joint of the TUM is free and a device which is called "torque unit" is equipped on each link of the TUM. The position-controllability of TUM is shown with a conventional control law. However, with the conventional method some of the state variables cannot be controlled. In this paper, a scheme is given to overcome the problem. The scheme involves generating trajectories for the links of TUM and using the trajectories as the desired ones in position-control. Simulation results with the scheme are shown.

This paper presents a dispersed-pulse codebook for CELP coder. This codebook generates an excitation vector by convoluting dispersion vectors with signed pulses in an algebraic codevector. The dispersion vectors are obtained through training so the coding distortion to be reduced. An objective evaluation result shows that the coding distortion with this codebook is smaller than that with an algebraic codebook. The dispersed-pulse codebook is applied to a 4 kb/s CELP coder. Subjective evaluation results show that: (1) the fundamental performance of the 4 kb/s coder is equivalent to that of G.726 32 kb/s coder, and (2) the performances of the 4k b/s coder under some error and background noise conditions are equivalent to those of G.729 8 kb/s coder.

An error correction approach which is based on a hidden Markov model (HMM) is proposed. The occurrence probability of a code sequence, which is delivered by the HMMs, is used as the measure for the maximum a posteriori probability (MAP) algorithm. The MAP algorithm is based on the assumption that the source is a discrete-time finite-state Markov process, and the HMM which models a Markov source is well suited for speech data. Therefore this combination would be useful for a speech coding system. The proposed approach is adapted to the code sequence quantized line spectrum frequency (LSF) parameters. When the code sequence is sent over a binary symmetry channel (BSC), the proposed approach with 16-state HMMs improves in code error rate and degradation of the cepstrum distortion by about 27% and 39% respectively for 3% random errors.

A new design concept of a manipulator is proposed, which is called torque-unit manipulator (TUM). The TUM was just born out of an idea of utilizing counter-torque, and its position-controllability has been shown theoretically. Hence, mechanical implementation and experimental examination are very important for the TUM to be in practical use. In this paper, experimental results are shown using a prototype TUM which is 2 degree-of-freedom and a discussion is given.

A necessary and sufficient condition has been shown for a set of base parameters to determine a inertial matrix to be positive definite for each configuration of a manipulator after continuous change of each joint variable of the manipulator is approximately considered as a finite set of discrete points. The condition enables us to judge if a set of estimated base-parameter values determines the inertial matrix to be always positive definite or not. A method also has been proposed to modify the estimated base-parameter values such that the set of them determines the inertial matrix to be always positive definite after it is judged not to do.>

A base parameter set as a minimum set of inertial parameters whose values can determine a dynamic model uniquely is investigated for a general parallel and perpendicular manipulator with rotational joints only. The notion of a base parameter is useful for an efficient and accurate identification of the manipulator dynamic model. A set of inertial parameters described in linear combinations of link parameters directly and completely in closed form is given and proved to constitute a base parameter set. It can be derived from this that the minimum number of inertial parameters whose values can determine the dynamic model is 7N-4 beta /sub 1/ (7N-4 beta /sub 2/-2 if the first joint axis parallel to the gravity vector), where N is the number of links in the manipulator, and beta /sub 1/ is the number of links connected by joints whose axes are always parallel to the first joint axis. After defining the base parameter, it is also shown that any base parameter set can be obtained from one base parameter set by a nonsingular linear transformation. The method adopted has the potential advantage of determining the relations between base parameters and manipulator motions.>

Base parameters (a minimum set of dynamic parameters whose values can determine a dynamic model uniquely) are investigated for general parallel and perpendicular manipulators with rotational and translational joints. The base parameters determine a very fundamental motion for manipulator dynamic models and are useful for identification of dynamic parameters and efficient algorithms to solve the inverse dynamics problem. Base parameters are described in terms of a linear combination of link inertial parameters, and the exact number of base parameters is shown. These results are extensions of the authors' previous results (1988) for parallel and perpendicular manipulators with rotational joints only.>

The base parameters (nonredundant parameters that can generate the dynamic equations of motion) are investigated for general parallel and perpendicular manipulators with only rotational joints. A set of parameters that are simple combinations of the link is proved to be the base parameters by analyzing the dynamic equations and making clear the redundancies of the link parameters of the manipulators. The results can be applied to parameter identification of the manipulator dynamic models and in algorithms for solving the inverse dynamic problem.>

The authors have developed a laser range finder (LRF) which enables a mobile robot to measure the distance to a natural object located 1-5 m ahead with an error less than 2%. The system uses a laser as weak as 1 mW, a safe level for human eyes, and is workable under bright daytime sunlight of about 100000 lx. This LRF can quickly process data and makes real-time measurements of objects located ahead. It features plural redundant range-measuring systems and a novel real-time signal. The effectiveness of the LRF system has been demonstrated under direct sunlight by an experimental model mounted with two CCD cameras and a semiconductor laser with output power of 1 mW (830 nm).>