In Bicycle Motocross (BMX) racing, a fast gate start is crucial for overall race performance (Rylands2014). The goal of this study was to (1) provide a better understanding of how cyclists effectively propel the bicycle during BMX gate start, and (2) identify pedalling variables which are good predictors of a fast start."

On all levels of rowing, a general rule is that you have to row together. Rowing together has no clear-cut definition. However, it is known that each rower has his or her own style, which can be registered in movement patterns and force curves. The big question is how to combine these individual styles such that the crew works together in the best way. The Dutch Rowing Federation showed interest in this topic, wanting to know how to adjust the rigging dimensions of the boat to allow the best racing performance. The goal of this thesis is to provide advice on what features of the rowing stroke should be synchronized and whether and how this could be promoted by individualized rigging. The theoretical foundation for this study was a literature study about the current knowledge on the rowing stroke and differences within and between individuals and crews. Current used measures on performance and synchronization of rowers were described, and finally a proposal was done for which methods to use in the ongoing of the study. Data was obtained from five female athletes of elite level, doing trials in a quadruple sculls of approximately 30 seconds at 30 SPM and 32 SPM in four different combinations. The strokes were identified and analyzed, based on performance and synchronization measures. Performance measured as Average Speed, Work per Stroke, Blade Losses, Velocity Fluctuation Losses and their respective and combined efficiencies. Synchronization measures were defined as Mean Standard Deviation of the Phase, Standard Deviation of the Time to Half Impulse and Standard Deviation of the Time to Half Work. The chosen synchronization measures were not completely independent. Standard deviations of time to half impulse and half work were found to be highly similar (r = 0.970). An opposite effect was found between kinematic synchronization and the other two, Mean Standard deviation of the Phase was not in line with the empirical rule that better synchronization leads to better performance. The kinetic and energetic measures did show this effect: Lower standard deviations of time to half impulse and time to half work meant higher average speed (r = −0.193) and higher Work per Stroke (r = −0.574). The best performing synchronization measure was time to half impulse synchrony. A drawback on this measure was that the sampling period was long, compared to the interpolated time differences. Athletes were found to achieve their half impulse moments in a consistent order. To find out whether it is possible to promote synchronization and thus performance by individualizing rigging, the oar angles at the time to half impulse were analyzed. This new measure correlated moderately (r = 0.624), meaning it quantifies more or less the same effect. The kinetic similarity actually worked better (r = −0.292 with Average Speed and r = −0.748 with Work per Stroke) than the synchronization measure. Similarity of half impulse angles enables the coach to adjust the rigging such that the timing should improve too. However, this should be tested in a follow-up study.

A model for the team time trial in road cycling is devised adn optimizations are caried out to find the most optimal strategy over different terain

The automotive industry is continuously improving the safety and comfort of the vehicles. To improve the safety and comfort of the vehicle more focus is put on improving driver assistance systems and also on making the vehicles more autonomous. In order for the safety systems to work properly and also to drive autonomously, it becomes essential that the vehicle has accurate knowledge of all the states of the vehicle. Two of such states are the roll and pitch angle. They are used to correct the images of a stereo camera, in roll control systems and for comfort assessment in autonomous vehicles. Measuring the roll and pitch angle is in practice problematic. Gyroscopes are mostly used to calculate the roll and pitch angle by integrating the angular rates with respect to time. If low quality gyroscopes are used, this leads to inaccurate calculation of the roll and pitch angle, because the measurements contain noise or bias accumulated during the integration process. To use these low quality gyroscopes, they need to be incorporated in an robust algorithm together with other sensors. Only then the roll and pitch angle can be estimated accurately. In this thesis a dynamic observer is developed, which has an internal vehicle dynamic model that calculates the tyre forces using an exponential tyre model. The performance of the observer is not only assessed using the true roll and pitch angle, but also compared against the performance of a kinematic observer. To test the performance of both observers various test manoeuvres were executed in IPG CarMaker, which is a highly advanced vehicle simulation environment. The manoeuvres consisted of rapid steering inputs and hard braking to execute large roll and pitch angles. Sensor noise was added to the inputs of the observers to simulate low quality sensors. In this thesis it has been shown that incorporating dynamics into an observer significantly increases its estimation performance and outperforms the kinematic observer during all manoeuvres when sensor noise was added to the inputs of the observers. The contribution of this thesis to the scientific field is that an exponential tyre model is used for the calculation of the roll and pitch angle in the internal vehicle dynamic model of the dynamic observer. Another contribution is that this thesis not only compares the performance of the dynamic observer against the real roll and pitch angles, but also against a kinematic observer, to see what the estimation improvement is when including dynamic relations.

Haptic feedback from the steering wheel is one of the most important cues for driver to vehicle interaction. The right feedback is provided by ensuring that the haptic controller provides the required steering feel. Steering feel assessment and design is divided into a subjective and objective approach. The subjective approach entails experiments on the proving ground during which steering parameters can be tuned by steering experts. However, using only subjective assessment is time-consuming, costly and non-repetitive. Since there is no direct method to tune the steering feel objectively, a driver model is required to find a mathematical justification in the mechanical interaction between driver and vehicle during steering. A 3-dimensional multibody arm model is constructed to investigate the influence of driving posture on the nonlinear steering response. It was found that the torque acting in the shoulder joint is higher than in the elbow. The relation between joint torque and joint angles is linear in the shoulder, whereas nonlinearities were found in the elbow joint. Nevertheless, a change of driving posture (i.e. a change of haptic interface) leads to a different steering response. Findings from the driver model were validated by two steering experiments. Muscle contraction was measured in order to analyse the forces acting on the joints. This study shows promise to lead to a different approach for tuning steering parameters. Further investigation and detailed experiments are required to convert this driver model into a method to tune steering feel objectively.

Instrumented treadmills and perturbations of the treadmill are commonly used for gait analysis and can provide real time biomechanical information and feedback of gait patterns and abnormalities. Force plates in the treadmill are combined with motion capture data and fed into a musculoskeletal model. High accuracy of the force plates is needed to give reliable feedback for gait analysis. The accuracy still needs to be tested under dynamic conditions, with the belt running. Also, inertial and gravitational forces are measured during perturbations as a result of the rotation and translation of the platform in which the force plates are positioned. This results in an error in the forces and moments as measured by the force plates, which is added up to the forces exerted by a subject. Inertia compensation models have been developed and showed promising results but have not been validated extensively. This study aimed to optimize and validate an inertia compensation model for perturbations on instrumented treadmills and validate the force measurements under dynamic conditions. It was shown that the treadmill can accurately measure the center of pressure (error = 1-6 mm), forces (error = 1-7 N) and moments (error = 0.5-4 Nm). A new calibration trial was found with higher sway accelerations which improved the inertia compensation model and left residuals forces and moments below 2 N(m). Moreover, it showed that using this inertia compensation model for pitch and sway trials led to a reduction of the kinetic residuals of up to 96% and values close to baseline measurements.

The development of the pole vaulting record is only improved by 1 centimeter over the last 25 years. Multiple studies show signs of different control strategies in elite pole vaulters, without pointing out what the cause of the differences is The aim of this research is to explore pole vaulting strategies by a control torque optimization. The optimization is performed for a simplified biomechanical model. The vaulter contains three segments: arms, a trunk including the head and legs. The joints are represented by torque actuators, located at the hands, shoulder joint and hip joint. The torque profile of each actuator is optimized. The optimization starts just after the pole is planted. It ends when the vaulter releases the pole. The pole length, pole stiffness, the vaulter’s length, the vaulter’s mass and the take-off angle are varied to discover the influence of these parameters on the control strategy. Three control strategies are found, as well as two power management strategies. Global trends are found. An increased pole stiffness, a decrease in length and mass of the athlete and a decreased take-off angle improved the performance. A possible optimal pole length is found.

Running-specific prostheses enable amputee athletes to perform at the highest level. However, current prosthesis design still impairs sprinting performance in multiple ways. An example is the constant mechanical stiffness of the prosthetic devices. The dynamic behaviour of the blade is determined by this property, but it is static and cannot change according to the gait phase-specific sprinting dynamics. During acceleration a different stiffness might be required as opposed to steady state running. Therefore, it is hypothesised that amputee athletes can improve their performance with prostheses that have a gait phase-specific stiffness. In order to investigate the effect of stiffness on amputee sprinting performance a novel and unprecedented modelling approached is used. Modelling is economical and straightforward in comparison to other research methods such as laboratory experiments. In this thesis, an extension of the established Spring-Loaded Inverted Pendulum model is proposed that qualitatively describes amputee sprinting motion. The Actuated Spring-Loaded Inverted Pendulum (ASLIP) is capable of predicting stable forwardly integrated sprinting motion with the inclusion of the start and acceleration phase. Optimisation of the model predicts that phase-specific spring stiffness leads to a significant time reduction on the 100m sprint for given physiological parameters. In general it can be said that a stiffer spring results in better performance. More specifically, the model benefits from a stiff spring during acceleration and a more compliant one in steady state. Although it has its limitations, the ASLIP model additionally provides a valuable insight into the mechanics of amputee sprinting. For example, it seems that optimal phase-specific stiffness is strongly dependent on biomechanical parameters such as touchdown angle, force angle and CoM velocity. Future work in this direction can provide a better understanding of the underlying mechanisms that determine amputee sprinting performance. The outcomes of this study suggest that amputee sprinters might be able to achieve a reduction in finishing time with prosthetic devices that have a phase-specific stiffness. The modelling approach used in this thesis is promising and lends itself well to investigate this opportunity in more detail.

During team time trials in road cycling changing schemes are used to spread the workload over the cyclists in the team. Models that provide predictions of race performance already exist for individual time trials. It is proposed that with a performance model for team time trials, the performance of different strategies can be compared and optimised. In literature combinations of mechanical resistance models and physiological models are used to determine the performance of individual time trials. The aerodynamic interaction between cyclists is very important to the effectiveness of a strategy. Coefficients of drag reduction between cyclists in a team time trial are presented in several studies, however most studies use groups of only four cyclists, which is not useful for a team time trial with eight cyclists. Only two studies report data for groups up to eight cyclists. These two models show different behaviour and are both used to asses the performance of strategies. Also two physiological models were used. In the model provided in this study the resistances are calculated from the kinematics resulting from the evaluated strategy. The mechanical resistance model, including the aerodynamic interaction model calculates the power required to perform the strategy. The physiological model calculates the physiology during the race, which determines if the cyclists are able to sustain the prescribed strategy. Genetic algorithm optimisation is used to optimise the strategy parameters, such as initial position and times spend in first position. The velocity is optimised for each evaluated strategy configuration. A convergence test was performed to determine the parameters for the genetic algorithm, which are used in the optimisation of strategy. Using the standard strategy, where cyclists only change from first to last position, different orders are compared. From this study it was determined that the mean velocity over a 30 km team time trial could be raised by a maximum of 0.228 m/s by improving the order, depending on the model configuration. It was found that the best performing orders were those where the mean performance difference of following cyclists was lowest. Two different strategies have been assessed where cyclists still always change from first, but not necessarily last position have been assessed on their performance. With those more complex strategies the mean velocity could be increased with 0.358 m/s over a 30 km team time trial. The model still lacks validity, but gives a relevant insight in the performance of different team time trial strategies. The validity can either improved by using track test to validate the drag reduction coefficients or by using power data from a team time trial to show that the model predicts realistic physiology. Of those two methods the last is preferred.

Bicycles connected to the internet present an opportunity for integrated accident detection and geolocation. Such a system can reduce the time it takes for help to arrive by automatically alerting predefined contacts with the location of the accident. I developed a systematic method for the practical implementation of bicycle accident detection in connected bicycles and present the performance of a prototype system. The method uses accelerometer and gyroscopic measurements as well as localization and velocity estimations. Supplementing existing research, a bicycle accident detection system is validated on normal cycling, edge cases, and three types of single bicycle accidents with constraints set by a bicycle manufacturer. Edge cases are movements of a bicycle that occur during regular usage, but can not be described by normal cycling. This method uses a data¬driven approach. For the prototype system, the input signals are collected during 71 different simulated accidents and 54 hours of normal cycling and edge cases. A three¬layer detection algorithm determines if an accident has occurred and sends the last known location to a set of predefined contacts. Multiple combinations of thresholds and classification algorithms are compared. This resulted in a prototype system with a K¬Nearest Neighbours classifier which detects 75% of accidents. Normal cycling and edge cases are correctly detected 99.997% of the time. From all warnings send, 85.7% are true accidents. The prototype system proves that the proposed method can be used to integrate reliable accident detection in connected bicycles. Bicycles with such a system automatically inform emergency contacts with a message containing the location of the accident, in a time where every second counts.

Current multi-DoF compliant manipulators are still rarely implemented in the industry because their range of motion (ROM) is limited as their designs are heavy and bulky or obtained by a serial set of multiple stacked flexure systems, which limits their compactness. The goal of this article is to overcome these limitations by considering them as an integrated multi-DoF compliant joint, either serial or parallel, and setting up a new method the Compliant Manipulator Design (COMAD)-method and investigate its performance. This method will combine the "Type synthesis of legs"-technique to include parallel kinematic solutions for the desired motion pattern whereafter the complete compliant solution space is obtained using the FACT-method. The method is applied for designing a 4-DoF-manipulator with a TTTR-motion pattern resulting in four new concepts composed of compactly aggregated wire flexures. After the concept selection, a demonstrator is manufactured which excellently possesses four decoupled motions with a relatively large ROM. This can be seen as a new milestone for designing multi-DoF compliant manipulators as it permits a larger ROM and better stiffness capabilities than those obtained from conventional methods because all compliant topologies are deflecting in series due to the parallel kinematic couplings within the multi-DoF flexure systems.

Part of the goal of Europe’s Strategy Vision Zero is to eliminate all severe cycling accidents in Europe by 2030. The majority of cycling accidents are single vehicle accidents; this term indicates the absence of collisions with other road participants and implies a fall of the cyclist. Research has shown that mainly elderly cyclists are victim to those accidents. An untested hypothesis is that their slowed motor responses are one of the main reasons behind this. This study aims to address this hypothesis by studying the influence of neural time delay on the lateral stability of bicycle-rider systems. In this study, the slowed motor responses are represented by single neural time delay values. The influence is quantified by the sizes of the identified basins of attraction of stability (BoA). The BoA contains the set of finite lateral disturbances for which stability is retained and is acquired via numerical integration. Binary threshold criteria are used to determine the stability of the solution. The bicycle-rider system consists of two components: a bicycle model and a rider model. The bicycle is modelled using the Whipple(-Carvallo) bicycle model with the set of non-linear equations derived by Basu-Mandal [2]. The rider is modelled using an implicit experimentally validated model from literature [31]. This model consists of a PID controller with full state feedback, neuro-muscular dynamics and, in this study, is extended to include nonzero time delay. The neural time delay value of a young cyclist has been based on literature [4]. The value is doubled to model an older cyclist. The control strategy of the young cyclist is identified using system identification techniques. The basins of the young and old cyclist are compared to study the detrimental effect of time delay on lateral stability in cycling. It declined over 80% when the time delay was doubled. The human’s ability to adapt its control to circumstances has been considered by repeating the control identification process for the rider which suffers from double the time delay. With respect to the young cyclist, a decline of over 50% was observed. Therefore, the results strongly support the hypothesis. Further research should focus on increasing complexity of the rider model to include preview and prediction. In this way, the influence of slowed motor responses can be mapped more clearly. A secondary objective of this thesis is the preliminary development of a steer assist control model to aid the elderly cyclist balance during cycling. This development builds further on a simple control model from literature [29] which uses roll angle feedback. As a result, a nonlinear velocity dependent roll rate feedback control law was developed. This control law yields a constant basin height over the commonly used velocity range of cyclists. This height indicates the maximum allowable steer rate perturbations the bicycle-steer assist system could handle and is approximately the same height as what was identified for a young cyclist. Future research is required for improving the steer assist. This means adding maximum allowable control torque, sensorial time delays and trajectory tracking

Brake squeal is a well know problem in the bicycle industry. Most of the time brake squeal occurs due to wear of the brake components and/or in certain environmental conditions (e.g. rain and dirt). Bicycle brake squeal is often solved by trial and error. Compared to automotive industry, there is not much research done on the fundamental cause of bicycle brake squeal. As a result, bicycle brands are not able to guarantee that their bicycles will not produce squeal noise over time. The goal of this graduation project is to get more insight into the fundamental cause of bicycle brake squeal and to find the crucial parameters that influence bicycle brake squeal.

Introduction: The BMX start is crucial for race performance, often measured by the time to the kink at 3.15 m from the start. Objective: This study aims to optimize the BMX SX gate start using predictive optimal control techniques, focusing on the effects of maximal crank torque and reaction time on performance. Method: Two models were used: The ‘upper extremities’ model analysed varying crank torques (250 Nm to 350 Nm) and reaction times (0.14 s, 0.16 s, 0.18 s). The ‘two legs’ model was assessed under a single condition to better reproduce crank torque and track experimentally measured kinematics. Results: Higher crank torques led to more forward initial positions, reduced recoil, and increased final velocities. The velocity of the start gate was a limiting factor initially, with timing and technique being crucial until the gate is halfway open. Reaction time variations showed minor effects on performance, and no strategy adaptation was needed within the tested range. The ‘two legs’ model accurately tracked experimental kinematics with low RMSE values. The predictive simulation with the ‘two legs’ model showed an improvement in kink time. The kink time for the predictive optimal control solution was 1.15 s compared to 1.23 s in the experimental trial. Conclusion: This framework for researching the BMX start using predictive optimal control offers a systematic basis for future research. Insights can improve training strategies focusing on technique, timing, and initial start position. Future research could explore the effects of leg strength, hip range of motion, and gear ratios or crank lengths on performance.