No description available.

The haptic device recreates the sense of touch by applying forces to the user. Since the device is “rendering” forces to emulate the physical interaction, the force control is essential for haptic devices. While a dedicated force/torque sensor can close the loop of force control, the additional equipment creates extra moving mass and inertia at the tool center point (TCP). Therefore, estimating the Cartesian force at the TCP has continuously been receiving attention over the past decades. The objective of this thesis project is to develop a real-time force estimation algorithm based on the proportional current-torque relationship with the dynamic modeling of the TAU haptic device. The algorithm can be further used for the force control of the device. The research questions of the thesis are: how to design and develop an algorithm for the TAU that used for Cartesian contact force estimation, how to set up the force estimation test bench and how to evaluate the results of the force estimation algorithm. In order to achieve the force estimation algorithm, a virtual environment is built to simulate the real-time haptic physics. Then an external force/torque sensor is installed at the TCP to get the measurement of the Cartesian force at the TCP. The force estimation algorithm calculates the Cartesian force at the TCP based on the current measurement of the DC motors at the six joints. The estimation result of the Cartesian force at the TCP is then compared with the force/torque sensor measurement to determine if the estimation algorithm is sufficiently accurate. The analysis of the estimation accuracy emphasizes the feasibility of Cartesian force estimation on the TAU haptic device. / En haptikenhet gör det möjligt att förmedla en känsla av kontakt i en virtuell värld genom att skapa krafter som motverkar en rörelse . Hur denna kraft skapas och kontrolleras är av stor vikt för att få den så verklighetstrogen som möjligt. Om man har en kraftsensor kan den användas till att utforma en kraftreglering med återkoppling, men på bekostnad av en ökad massa och tröghet vid användarens hand. Detta har medfört ett ökat intresse under de senaste åren för att på olika sätt försöka uppskatta den kraft som återkopplas till användaren utan att behöva en kraftsensor. Målet för detta examensarbete är att utveckla en algoritm för att uppskatta en kontaktkraft i realtid baserat på antagandet att motormomentet är proportionellt beroende av strömmen. Algoritmen kan sedan användas för att konstruera en sluten reglerloop med kraftåterkoppling för en haptisk enhet. Forskningsfrågorna som behandlas i detta examensarbete är;  hur kan vi utforma en algoritm för estimering av kontaktkrafter för haptikenheten TAU  hur kan vi utforma en experimentell försöksuppställning för mätning av de verkliga kontaktkrafterna från TAU vid kontakt.  hur kan vi använda resultaten från experimenten för utvärdering av algoritmen För testning och utvärdering av algoritmen har en virtuell värld skapats för att efterlikna en simuleringsmiljö som haptikenheten är tänkt att användas i. En kraftsensor har monterats under det verktyg som användaren håller i när enheten används när ett typiskt ingrepp ska övas i en simulator, t.ex. borrning i en tand. Vid experimenten beräknar algoritmen den uppskattade kontaktkraften som användaren känner baserat på den uppmätta strömmen för de sex motorer som aktiveras av kontakten. Dessa beräknade värden har sedan jämförts med de från kraftsensorn uppmätta för att avgör om algoritmen är tillräckligt noggrann. Analysen visar att noggrannheten är tillräckligt bra för att vara en lovande ansats till att användas för kraftuppskattning vid reglering av kontaktkraft för haptikenheten TAU.

No description available.

<p>The transmission is probably the drivetrain component with the greatest impact on driveability of an automatic transmission equipped vehicle. Since the driver only has an indirect influence on the gear shift timing, except for situations like kick-down accelerations, it is desirable to improve shift quality as perceived by the driver. However, improving shift quality is a problem normally diametrically opposed to minimizing transmission clutch energy dissipation. The latter has a great impact on transmission lifetime, and has to be defined and taken into consideration along with the notion of shift quality. The main focus of this thesis is the modeling of a drivetrain of an automatic transmission vehicle, and the implementation in MatLab/Simulink, including the first to second gear upshift. The resulting plant based on the derived equations is validated using data from a test vehicle equipped with a torque sensor located at the transmission output shaft. The shaft torque is more or less proportional to the driveline jerk, and hence of great interest for control purposes. Control strategies are discussed and a PID controller structure is developed to control the first to second gear upshift, as opposed to the traditional open-loop upshift control. Furthermore, the proposed controller structure uses the transmission output torque and the differential speed of the engaging clutch as inputs, to control the clutch pressure and the engine output torque, respectively. The structure is unsophisticated and transparent compared to other approaches, but shows great theoretical results in terms of improved shift quality and decreased clutch wear.</p>

<p>This is a thesis for a Bachelor Degree Project, performed in the subject Mechanical</p><p>Engineering. The students Roger Malmberg and Simon Hagberg have carried out a</p><p>design project on behalf of the recently established company J&D Assisting systems,</p><p>located in Halmstad.</p><p>The project consisted in developing J&D's first prototype of a power assisting solution</p><p>for wheelchairs. A power assisted wheelchair combines human power, which is delivered</p><p>by the arms through the pushrims, with electrical motors, which are powered by a battery.</p><p>The power assisted wheelchair is aimed at customers, who have used a regular</p><p>wheelchair for a long time, but who have become weaker or just need additional power</p><p>when driving uphill. This kind of wheelchair will provide additional power for users,</p><p>which will spare their wrists, elbow and shoulders. The product is torque sensor free and</p><p>instead it relies on the velocity. Engines and gearboxes from the company All motion was</p><p>a requirement. The construction could not impair the wheelchair's trafficability and the</p><p>performance would at least match up with the performance of the first prototype. To build</p><p>a working prototype was a part of the task. The work was early focused on the specific</p><p>wheelchair Etac Next. At the same time, the result should be, as much as possible,</p><p>suitable for the most common wheelchairs.</p><p>The result is a design where the engine packet is assembled in a 90° angle towards the</p><p>wheelaxle. In the angle, the power is transferred by bevel gears, assembled on shafts</p><p>supported by ball bearings. Then, the force is transmitted via a modified wheel axle to a</p><p>structure mounted outside the hub. Eight stokes transfers the force to the hand rims.</p><p>An operational prototype has been built and then been assembled on the wheelchair Etac</p><p>Next. The part mounted outside of the wheel has got a plastic hood to cover up and to</p><p>protect the inner parts. The plastic hood has been produced with SLS technology.</p>

The transmission is probably the drivetrain component with the greatest impact on driveability of an automatic transmission equipped vehicle. Since the driver only has an indirect influence on the gear shift timing, except for situations like kick-down accelerations, it is desirable to improve shift quality as perceived by the driver. However, improving shift quality is a problem normally diametrically opposed to minimizing transmission clutch energy dissipation. The latter has a great impact on transmission lifetime, and has to be defined and taken into consideration along with the notion of shift quality. The main focus of this thesis is the modeling of a drivetrain of an automatic transmission vehicle, and the implementation in MatLab/Simulink, including the first to second gear upshift. The resulting plant based on the derived equations is validated using data from a test vehicle equipped with a torque sensor located at the transmission output shaft. The shaft torque is more or less proportional to the driveline jerk, and hence of great interest for control purposes. Control strategies are discussed and a PID controller structure is developed to control the first to second gear upshift, as opposed to the traditional open-loop upshift control. Furthermore, the proposed controller structure uses the transmission output torque and the differential speed of the engaging clutch as inputs, to control the clutch pressure and the engine output torque, respectively. The structure is unsophisticated and transparent compared to other approaches, but shows great theoretical results in terms of improved shift quality and decreased clutch wear.

This is a thesis for a Bachelor Degree Project, performed in the subject Mechanical Engineering. The students Roger Malmberg and Simon Hagberg have carried out a design project on behalf of the recently established company J&D Assisting systems, located in Halmstad. The project consisted in developing J&D's first prototype of a power assisting solution for wheelchairs. A power assisted wheelchair combines human power, which is delivered by the arms through the pushrims, with electrical motors, which are powered by a battery. The power assisted wheelchair is aimed at customers, who have used a regular wheelchair for a long time, but who have become weaker or just need additional power when driving uphill. This kind of wheelchair will provide additional power for users, which will spare their wrists, elbow and shoulders. The product is torque sensor free and instead it relies on the velocity. Engines and gearboxes from the company All motion was a requirement. The construction could not impair the wheelchair's trafficability and the performance would at least match up with the performance of the first prototype. To build a working prototype was a part of the task. The work was early focused on the specific wheelchair Etac Next. At the same time, the result should be, as much as possible, suitable for the most common wheelchairs. The result is a design where the engine packet is assembled in a 90° angle towards the wheelaxle. In the angle, the power is transferred by bevel gears, assembled on shafts supported by ball bearings. Then, the force is transmitted via a modified wheel axle to a structure mounted outside the hub. Eight stokes transfers the force to the hand rims. An operational prototype has been built and then been assembled on the wheelchair Etac Next. The part mounted outside of the wheel has got a plastic hood to cover up and to protect the inner parts. The plastic hood has been produced with SLS technology.

No description available.

High precision tightening of nuts and bolts together with traceability are important in many industrial assembly lines. To achieve this the nutrunner needs to accurately measure the torque which is applied to the nut, process the signal and provide the information to the controller that controls the tightening process. This is done by having a strain gauge in form of a Wheatstone bridge connected to the tightening shaft. When an excitation voltage is applied to the bridge the applied torque to the shaft can be measured in form of a voltage difference. This voltage is amplified, filtered and converted to a digital signal, this is referred to as the signal chain. Atlas Copco has provided an example of how the signal chain looks in today’s application. The signal chain consists of a gain stage and a filter stage, and the analog-to-digital conversion process is performed internally in an MCU together with several advanced digital filters. The purpose of this thesis is to analyse this signal chain, it’s performance in regards to noise and investigate if the chain can be redesigned with the same or better noise performance with other components. It should also be investigated if the conversion process can be moved from the MCU to an integrated circuit component to reduce the effects of noise from the tool motor. Hence, in addition to noise, other specifications such as power supply and physical footprint is also considered in the thesis. The goal is to define a process on how to analyse the noise, precision, speed and footprint in a front end signal chain. In addition to that, one or more alternative signal chains should be presented if the requirements of the front end can be fulfilled. A lot of effort went into researching how noise impacts a signal chain to get a thorough understanding on how to improve/rebuild an already functioning signal chain. The result was a working process on how to analyse the noise in a front end signal chain like the one described above, together with a generic noise simulation model in LTSpice which can be used if a component does not have a spice model. With the model a few alternative signal chains were considered which fulfills the noise requirements and the best performing alternative was built on a PCB in KiCAD. However, the physical PCB has not been tested due to the limited timeframe of the project and therefore only calculations and simulations act as the verifying element of the function. / Högprecisionsåtdragning av skruvar och bultar är en viktig del av många industriella tillverkningsprocesser. I detta ingår ofta spårbarhet som en viktig del för att kunna kvalitetssäkra processerna. För att åstadkomma detta måste skruvdragaren kunna mäta det moment som appliceras vid en åtdragning, bearbeta denna signal och tillhandahålla den till kontrollenheten som styr åtdragningsprocessen. Momentmätningen görs med en töjningsgivare, ofta av typen Wheatstonebrygga, som kopplas till verktygets axel. När en excitationsspänning kopplas till bryggan kan momentkraften i axeln mätas i form av en spänningsskillnad. Denna analoga signal blir sedan förstärkt, filtrerad och omvandlad till en digital signal. Denna process benämns som signalkedjan. Företaget har tillhandahållit ett exempel på hur en sådan signalkedja ser ut i en av deras nuvarande verktyg. I dagens utförande sker signalomvandlingen internt i en mikrokontroller, där den också filtreras med digitala filter. Syftet med denna avhandling är att analysera signalkedjan, dennas prestation i förhållande till brus, och undersöka ifall signalkedjan kan återskapas med samma eller bättre brusegenskaper med andra komponenter. Det undersöks även om signalomvandlingen kan flyttas från mikrokontrollern till en integrerad krets-komponent för att minska signalens påverkan från brus från verktygets motor. Som led i detta kommer även kretsens fysiska fotavtryck undersökas då det styr var på verktyget kretsen kan monteras. Målet är att definiera en process för att analysera brus, precision, hastighet och fotavtryck i ett signalgränssnitt av denna typ. Utöver detta skall en eller flera förslag till alternativa signalkedjor presenteras om de kan uppfylla kraven på gränssnittet. Mycket ansträngning gick till att undersöka hur brus påverkar en signalkedja för att få en grundlig förståelse av hur man kan förbättra och/eller bygga om en befintlig signalkedja. Resultatet blev en fungerande teoretisk analysprocess av brus i en signalkedja i ett gränssnitt av den typen som beskrivs ovan. Ytterligare resultat var en generell brussimuleringsmodell i LTSpice som kan användas då en komponent saknar Spice-modell. Med hjälp av modellen utvärderades några alternativa signalkedjor utifrån deras brusegenskaper och utifrån det bästa alternativet togs en PCB-layout fram i KiCad. Några tester på en fysisk krets har dock inte gjorts då tidsramen för projektet inte tillät tillverkning av kretskortet. Därför utgår utvärderingen av kretsens funktion enbart från teoretiska beräkningar och simuleringar.

<p>A power assisted wheelchair combines human power, which is delivered by the arms through the pushrims, with electrical motors, which are powered by a battery. Today’s electric power assisted wheelchairs use force sensors to measure the torque exerted on the pushrims by the user. The force sensors in the pushrims are rather expensive and this approach also makes the wheels a little bit clumsy. The objective with this project is to find a new, better and cheaper solution that does not use expensive force sensors in the pushrims. The new power assisted wheelchair will instead only rely on its velocity, which is measured with rotational encoders, as feedback signal and thereby the project name “Torque Sensor Free Power Assisted Wheelchair”. </p><p> </p><p>The project consisted of two main parts; an extensive construction part, where an ordinary joystick controlled motorized wheelchair has been rebuild to the new power assisted wheelchair without torque sensors and a development part, where different torque sensor free controllers has been designed, simulated, programmed and tested.</p><p>The project resulted in a torque sensor free power assisted wheelchair, where the final implemented design is a proportional derivative controller, which gives a very good assisting system that is robust and insensitive to measurement noise. The proportional derivative control design gives two adjustable parameters, which can be tuned to fit a certain user; one parameter is used to adjust the amplification of the user’s force and the other one is used to change the lasting time of the propulsion influence.</p><p>Since the new assisting control system only relies on the velocity, the torque sensor free power assisted wheelchair will besides giving the user assisting power also give an assistant, which pushes the wheelchair, additional power. This is a big advantage compared to the pushrim activated one, where this benefit for the assistant is not possible.</p>