International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An original design is presented for a system capable of measuring the relative angle of a flat surface using reflected ultrasonic wave pulses. No physical contact with the surface is necessary. The measurement range is from 0 to 54 degrees. Theoretical resolution is 5 minutes of arc, with actual measured resolution of approximately 20 minutes of arc. The system has performed successfully in limited flight tests, is capable of rates up to 80 angle measurements per second, and has a solid-state memory recording capacity of 24,000 bytes. The measurements are time-tagged as they are recorded and may be transferred to a personal computer at a later time over a standard RS-232 serial communications link. The system is small (approx. 6 by 4 by 1.5 inches) and uses two standard 9-volt batteries as its power source.

This master’s thesis deals with calibration of incremental encoders. Introduces basic principles and terms in the field of rotary encoders and its calibration. The first part describes angular displacement sensors. Especially it focuses on optoelectrical incremental encoders. It also includes market research of very high-accuracy encoders. The second part contains description of precision calibration techniques with uncertainty to the thousandth of an arc-sec level. In the last part, the development of a calibration stage is presented and consequently the error map of an encoder is obtained.

Since the dawn of the space race, satellites have grown rapidly in complexity and shrunk equally rapidly in size. Most of them contain an Attitude Determination and Control System (ADCS) on board for pointing and detumbling manoeuvres. These intricate systems are designed for an outer space environment, hence, phenomenon otherwise abscent in space, such as gravity and aerodynamic drag present a challenge in validating these systems on Earth. The gimbal suspension testbed aims to provide a 3 Degree of Freedom (DoF) suspension where the mounted satellite under test can rotate about either axis. The suspension induces disturbance torques that must be modeled in order for the testbed to be characterized. This is accomplished by formulating the necessary gimbal dynamics, bearing friction, aerodynamic and Center of Mass (CoM) displacement torque model. This yields a relationship from which all torques present in the system can be expressed in terms of the angles, angular velocities and angular accelerations of the gimbal frames. By measuring the angles and obtaining the velocities and accelerations through numerical differentiation, the torques that correspond to a certain motion can be calculated. Furthermore, the thesis covers the iterative design of the gimbal suspension and all of its constituents, the angular measurement method and a Finite Element Method (FEM) simulation to estimate deformations. The result is presented in terms of a simulation that validates the models by predicting its behaviour for certain movement. The final result is a series of characterization plots that tells the user of the gimbal testbed how much torque must be produced by the CubeSat ADCS in order to operate it. / Sedan begynnelsen av rymdkapplöpningen har satelliter snabbt ökat i komplexitet och lika snabbt minskat i storlek. De flesta satelliter har ett attitydsbestänings- och kontrollsystem (ADCS) ombord för att kunna utföra vissa manövrar. Dessa system är designade för rymdmiljön, därför kan fenomen som annars är frånvarande i rymden, så som gravitation och luftmotstånd, innebära en utmaning då man önskar att validera systemet på jorden. Gimbalupphängningen förmedlar rotation med tre frihetsgrader där satelliten under test kan rotera kring alla tre axlar. Upphängningen inducerar störmoment som måste modelleras för att den ska bli ordentligt karaktäriserad. Detta åstadkoms genom att formulera gimbalens dynamiska förhållanden, kullagerfriktion, luftmotstånd och masscenterförflyttning. Dessa samband kopplar samman alla moment som är närvarande i systemet som funktion av gimbalramarnas vinklar, vinkelhastigheter och vinkelaccelerationer. Genom att mäta vinklarna och erhålla vinkelhastigheter och vinkelacceleration genom numerisk derivering kan momenten som motsvarar den uppmätta rörelsen beräknas. Dessutom presenteras den iterativa designen av gimbalupphängningen och alla dess beståndsdelar, vinkelmätningsmetoden och en finita elementmetodssimulering för att uppskaffa deformationer. Resultatet presenteras i form av simuleringar som validerar modellen genom att förutspå dess beteende för viss rörelse. Det slutgiltiga resultatet är en serie av karaktäriseringsgrafer som förmedlar till användaren just hur mycket moment dess CubeSats ADCS måste producera för att kunna använda gimbalupphängingen.