Information and Systems Science
　　The Mechanical Engineering Laboratory has a long history of research on Intelligent Transport Systems (ITS), beginning in the 1960s. Recent activities include work on lateral control algorithms for vision-based vehicles and longitudinal control algorithms for platoons. Experiments on lateral control for lane changing, obstacle avoidance, and lane following have been conducted with a full scale test vehicle on a test track, using an algorithm whose key feature is the use of whole references in the field of view (Fig.1). Studies of cooperative driving in platoons, compatible with both safety and energy-saving requirements, have also been made. Merging is a form of cooperative driving, and simulations of longitudinal control on merging have been made towards the design of optimal merging control algorithms for platoons on a ramp and in traffic. Design studies of algorithms for cooperative driving between vehicles in formation (like a school of fish or a flock of birds) have been made and will be evaluated using full-scale test vehicles on a test track in a few years.
　
Fig.1 Lane Changing (Example).
　
Topics in Optical Engineering
　　A new interferometer for mirror testing using a synthesised scatter plate has been developed, and its fringe resolution shown to be very much improved compared to conventional scatter plate interferometers (Fig.2). Computer simulations predicting the experimental results have also been developed.
　
Fig.2 Electron beam fabricated scatter plate interferogram.
　
　　A new phase shifting algorithm which compensates for both non-linear phase shifts and higher order harmonics in the fringe signal has been applied to a Ronchi interferometer for measuring highly aberrated wave fronts. The dynamic range was found to be improved by a factor of three compared to conventional methods.
　
Self-reconfiguring algorithms for 3-D structures
　　A reconfiguration algorithm for 3-D structures composed of many identical units has been developed. The algorithm is distributed through the units, each of which can change its connections to others on its own, and has a microprocessor and local communication channels. Each unit has identical software and can play any role in the structure. The algorithm enables the units to transform into any desired structure from an arbitrary initial state. A stochastic relaxation process, built into the algorithm, enables the system to converge to the target structure by searching for the required movement of units over many degrees of freedom. Applications of the system include autonomous planetary exploration vehicles or satellite antennae. Transported in compact folded form, the system developed in this work will allow them to deploy to the correct structure when operating and repair themselves if they are damaged. A simulation showing a self-reconfiguration sequence is shown in the Figure. The target structure is a 12-unit box which is successfully constructed in a decentralised manner. [61]
　
Fig.3 Simulation of reconfiguration process.
　
FDL - A new language for machine design
　　A constraint-based object oriented language called FDL has been developed for machine design. It has the capability to dynamically modify its own structure so that it can solve problems involving unpredictable design model structure changes. It was found to be not yet flexible enough to solve all dynamically changing problems and so a set of bio-genetic algorithms - by which further sophisticated object modification is possible - was introduced. These algorithms include structure merging, dynamic inheritance, object division, object apoptosis, and configuration operators. The structure merging operation creates a new object by merging two objects, where the set of slots and constraints of the new object is derived from the union of the two original objects. The Figure shows a gear drive in which a new pair of gears has been introduced by the structure merging operation. The dynamic inheritance mechanism enables an instance object to refer class objects dynamically when necessary, object division is used to divide an object without information loss, object apoptosis is used to selectively delete objects, and the configuration operator is for automatic object reorganization. [62]
　
Fig.4 Assembly by Structure Merging.
　
Advanced aerospace control technologies
　　A DC-9 aircraft belonging to the NASA Lewis Research Center was used for a series of microgravity experiments. During more than 200 parabolic flights, two research topics were investigated: bubble dynamics and boiling heat transfer in micro-gravity. In the bubble dynamics experiment, the photochromic method was used to visualise detailed flow patterns around growing gas bubbles in silicon oil. The experiments showed that the size and frequency of detachment of the bubbles are affected by fluctuations in gravity. In the boiling experiment, the thickness of the liquid film beneath the growing bubbles was successfully measured using a laser focus displacement meter. Images obtained with a high-speed camera showed that, unlike in boiling under normal gravity, bubbles grow through coalescence on the heating surface. Identifying the contribution of buoyancy to the bubble detachment mechanism and heat/momentum transfer in boiling is essential not only for developing techniques for processing highly homogeneous materials in space, but also for improving the efficiency of ground-based heat exchangers. [57,58]
　
Fig.5 Bubble Formation in Microgravity Boiling.

---

produced by General Research Counselor