Simple Obstacle Avoidance Algorithm for Rehabilitation Robots

The efficiency of a rehabilitation robot is improved by offering record-and-replay to operate the robot. While automatically moving to a stored target (replay) collisions of the robot with obstacles in its work space must be avoided. A simple, though effective, generic and deterministic algorithm for obstacle avoidance was developed. The algorithm derives a collision free path of the end-effector of the robot around known obstacles to the target location in O(n) time. In a case study, using the rehabilitation robot ARM, the performance of the algorithm was tested. As was a newly human-machine-interface offering this record-and-replay functionality to the use

The water acceptance of wrapped subsurface drains

The water acceptance of subsurface, agricultural pipe drains is largely determined by the hydraulic conductivity of the surrounding zone. If this zone consists of soil with a poor structural stability, such drains must be wrapped with an envelope to control the rate of pipe sedimentation while safeguarding easy access of water. The studies were made to elicidate the effects of envelope specifications on these requirements.Envelope response was observed in analogue models, for cohesionless, and weakly cohesive, very fine sandy soils. Cohesionless soils were stabilised best by "thin" envelopes. Water access was easy and was not a factor of importance in design. In weakly-cohesive soils, the capability of envelopes to meet the requirements was quantified using an "Envelope Suitability Index" (ESI). Both soil type and envelope type had a significant effect on ESI. Nevertheless, analogue model tests were of limited value because the findings could not be compared with field observations.A field survey was made of grade lines of 184 drains and of soil invasion and sedimentation patterns, root penetration and other phenomena in these drains. They were wrapped with various envelope types and installed in weakly-cohesive, very fine sandy soils in three experimental fields in The Netherlands. Over 9600 m of drain length were inspected. The rate of pipe sedimentation differed significantly between the experimental fields. The particle retention capability of envelopes was associated with the effective opening size of their pores, "O 90 ". The mechanisms of soil invasion into drains and the observed sedimentation rates differed from those predicted in analogue models. Generally, envelope specification had no significant effect on drainage resistance; only in cases where drains were also used for subirrigation did "voluminous" envelopes have significantly lower drainage resistances than "thin" ones.Cores, containing wrapped drain sections with the surrounding soil were sampled at 45 locations. All sections had been functioning in weakly-cohesive, fine-sandy soils for a period of 5 years. The effect of soil and envelope specification on the flow of soil particles near the drains was investigated by microgranulometric analysis. Generally, the finest soil particles were found to be concentrated near the soil/envelope interface. This tendency was largely accounted for by the particle size distribution of the soil. A "natural soil filter" had only developed in a few instances. The envelopes improve stability through supporting the soils rather than through acting as filters. The cores were also examined by x-ray computerised tomography (CT) through 50 adjacent slices. This yielded three dimensional (3D) mappings of the most permeable areas inside the drain envelopes and surrounding soils that convey most of the water to the drains. A finite element model was used to study the effect of radial soil heterogeneity around a subsurface drain on the water table height. Water flow and envelope clogging were found to be quite heterogeneous and were mainly determined by soil structural features. Soil structural stability is therefore the main determinant of the service life of wrapped drains. The physical effect of an envelope on physical soil/envelope interactions is less important than is generally assumed. On the contrary, soil properties are crucial

Design of a Dynamic Arm Support (DAS) for gravity compensation

The Dynamic Arm Support, or briefly the Das, is a new medical device that serves to compensate for lost arm function of the severely disabled. The target group suffers from insufficient muscle force to move its arms over the usual Range of Motion (RoM). The purpose of the Das is to assist its user during Activities of Daily Living (ADL) by eliminating gravity acting on the upper limb and enabling the limb to move freely. The development of the Das is presented and discussed, focusing on the modular parts, working principle, unique features, and technical performance as well as results for the target group

Verslag van een studiereis naar Roemenie (28 september - 10 oktober 1981)

Het doel van de studiereis was tweeledig, namelijk kennis.nemen van de problemen op het gebied van de drainage, en onderzoeken of er mogelijkheden zijn tot samenwerking op het gebied van de ontwikkeling van nieuwe, betere drainagefiltermaterialen. In het programma waren bezoeken opgenomen aan verschillende· instituten, lokale proefstations, drainage-objecten en een collectief bedrijf

Soil particle size distributions related to subsurface drainage systems in the Netherlands, the United States and Canada

In order to check the state of subsurface drain/envelope combinations, several dig-ups were made in the State of Michigan (United States), the Province of Ontario (Canada) and the southwestern part of the Netherlands, These opportunities were used to sample soil material in the vicinity of the pipe as well as sediment inside. No preparatory moves were made as regards sample containers, sample preservation etc., so all sampling activit1es have been fully incidental in their nature

Verslag van een studiereis naar de Verenigde Staten, 5 december-17 december 1982

Beknopte weergave van de in december 1982 gehouden International Drainage Workshop en het National Drainage Symposiu