Inverse Dynamics Method Research Articles

A Data-Driven Adaptive Method for Attitude Control of Fixed-Wing Unmanned Aerial Vehicles

In this paper, a real-time online data-driven adaptive method is developed to deal with uncertainties such as high nonlinearity, strong coupling, parameter perturbation and external disturbances in attitude control of fixed-wing unmanned aerial vehicles (UAVs). Firstly, a model-free adaptive control (MFAC) method requiring only input/output (I/O) data and no model information is adopted for control scheme design of angular velocity subsystem which contains all model information and up-mentioned uncertainties. Secondly, the internal model control (IMC) method featured with less tuning parameters and convenient tuning process is adopted for control scheme design of the certain Euler angle subsystem. Simulation results show that, the method developed is obviously superior to the cascade PID (CPID) method and the nonlinear dynamic inversion (NDI) method.

Adaptive Neural Network‐Based Satellite Attitude Control by Using the Dynamic Inversion Technique and a VSCMG Pyramidal Cluster

The paper presents an adaptive system for the control of small satellites’ attitude by using a pyramidal cluster of four variable‐speed control moment gyros as actuators. Starting from the dynamic model of the pyramidal cluster, an adaptive control law is designed by means of the dynamic inversion method and a feed‐forward neural network‐based nonlinear subsystem; the control law has a proportional‐integrator component (for the control of the reduced‐order linear subsystem) and an adaptive component (for the compensation of the approximation error associated with the function describing the dynamics of the nonlinear system). The software implementation and validation of the new control architecture are achieved by using the Matlab/Simulink environment.

Mapping Heterogeneous Elastic Property Distribution of Soft Tissues Using Harmonic Motion Data: A Theoretical Study

Characterizing heterogeneous elastic property distribution of soft tissues is of great importance in disease detection. In this paper, we investigate an inverse approach to map the heterogeneous material property distribution of soft solids using harmonic motion data. To examine the feasibility of this approach, a number of numerical examples are presented. We observe that the shear modulus distribution is recovered well using harmonic motion measurements. Compared to the static inverse approach, the proposed dynamic inverse method improves the quality of the recovered shear modulus distribution significantly. We also study the influence of the uncertainty in the driving frequency on the reconstruction results and observe that the influence is not very significant in recovering the shape of the inclusion. The proposed inverse algorithm has potential to be a promising tool to diagnose diseases in clinical medicine.

The relationship between knee muscle strength and knee biomechanics during running at 6 and 12 months after anterior cruciate ligament reconstruction

BackgroundKnee joint kinematics and kinetics during running recover at 12 months, not 6 months, following anterior cruciate ligament (ACL) reconstruction surgery. Knee muscle strength is a criterion used to assess an individual’s readiness to return-to-sports (RTS); however, the relationship between knee muscle strength and knee biomechanics is unclear. This study investigated the relationship between knee muscle strength and dynamic knee biomechanics during running at 6 and 12 months after ACL reconstruction surgery. MethodsKnee joint kinematics and kinetics during running were analyzed in 21 patients (10 males, 11 females) who underwent ACL reconstruction for a unilateral ACL deficiency. Kinematics and Kinetics were measured by three-dimensional motion analysis system, and Knee flexion angle was calculated using Point cluster technique and internal extension moment was calculated by the inverse dynamics method. Patients were compared to a control group matched by age, height and weight. Isokinetic knee extension and flexion strength in ACL-reconstructed patients were measured at 6 and 12 months postsurgery, by separated gender. ResultsKnee flexion angle was significantly lower in ACL patients at 6 months postsurgery compared to the control group (F (2, 62)=5.78, P=0.014). There were significant lower peak knee flexion angles in male groups than female (F (1, 62)=6.33, P<0.01). Knee extension moments were significantly lower in both male and female ACL patients compared to the control group at 6 and 12 months postsurgery (F (2, 62)=12.05, P<0.01(6 months), P=0.034(12 months)), and there were significant correlations with knee extension moments and maximum torque of knee extension/flexion (P<0.05). At 12 months after surgery, knee joint kinematics in ACL patients were restored. Both peak knee angle and knee extension moment were significantly associated with maximum knee extension/flexion torque values in female patients at 12 months postsurgery. ConclusionsDynamic knee biomechanics during running were not restored 6 and 12 months after ACL reconstruction both male and female. It is necessary to strengthen knee extension and flexion muscles to restore knee kinetics during running, especially female patients.

Minimum Time Overtaking Problem of Vehicle Handling Inverse Dynamics Based on Two Kinds of Safe Distances

Overtaking accidents caused by improper operations performed by a driver occur frequently. However, most studies on overtaking safety have neglected research into driver control input. A novel method is proposed to obtain the driver control input during the overtaking process. Meanwhile, to improve the safety of overtaking, two types of safe distances, and the time of the overtaking are considered. Path constraints are established when considering the two types of safe distances. An optimal control model is established to solve the minimum time maneuver under multiple constraints. Using the Gauss pseudospectral method, the optimal control problem is converted into a nonlinear programming problem, which is then solved through sequential quadratic programming (SQP). In addition, the effectiveness of the proposed method is verified based on the results of a Carsim simulation. The simulation results show that by adopting an inverse dynamics method to solve the manipulation problem of the vehicle’s minimum overtaking time, the manipulation capability of a vehicle in completing an overtaking safely within the minimum time can be obtained. This method can provide a reference for research into the active safety of manned and unmanned vehicles.

Initial balance in human standing postures: Roles of the joint mechanisms.

The static initial postures of standing before applying perturbations may affect the maintenance of postural balance. The goal of this article was to find the stable set of postures and then determine the roles of joint mechanisms. The set of posture was defined in a biomechanical model based on three joint angles of the lower limbs. Optimized inverse dynamics method was used to solve for muscle forces in a precise model of the human musculoskeletal system posed in 4096 static sets of posture using AnyBody software. Results showed that the overall body muscular activity in standing is reduced by knee flexion. Moderate knee angles between 20° and 60° provided safer postures against possible perturbations because of higher collaboration levels of the joint mechanisms. About 36% of the overall postural infeasibilities were attributed to the inability of the ankle muscles to more sustain the exerted loads. Although the roles of the joint mechanisms were closely dependent on the postures, there was no direct relation between the joint kinematics and activation levels of their supporting muscles. Lower extremity muscle groups collaborate to maintain the balance in a considerable number of static postures.

An Improved Nonlinear Dynamic Inversion Method for Altitude and Attitude Control of Nano Quad-Rotors under Persistent Uncertainties

Nonlinear dynamic inversion (NDI) has been applied to the control law design of quad-rotors mainly thanks to its good robustness and simplicity of parameter tuning. However, the weakness of relying on accurate model greatly restrains its application on quad-rotors, especially nano quad-rotors (NQRs).NQRs are easy to be influenced by uncertainties such as model uncertainties (mainly from complicated aerodynamic interferences, strong coupling in roll-pitch-yaw channels and inaccurate aerodynamic prediction of rotors) and external uncertainties (mainly from winds or gusts), particularly persistent ones.Therefore, developing accurate model for altitude and attitude control of NQRs is difficult. To solve this problem, in this paper, an improved nonlinear dynamic inversion (INDI)method is developed, which can reject the above-mentioned uncertainties by estimating them and then counteracting in real time using linear extended state observer (LESO). Comparison with the traditional NDI(TNDI) method was carried out numerically, and the results show that, in coping with persistent uncertainties, the INDI-based method presents significant superiority.

Modeling and control of a flapping wing robot

The dynamics and control of a flapping wing robot are studied in this paper which helps to develop a complete dynamic model for the robot consisting of tail effects and also enhance the path tracking control of the robot. In the first part of the paper, the aerodynamic model of the wings is presented, and an aerodynamic force model for the tail is introduced which includes the leading edge suction effects. An experiment is also carried out on a flapping wing robot in a laboratory environment to evaluate the forces on the tail and its result will be compared with the results of the model presented for the tail. In the second part, a controller is designed for the robot. This controller uses the nonlinear dynamic inversion method to solve the nonlinear equations of the control system. The experimental results of the tail forces agree well with the theoretical predictions and reveal that the tail aerodynamics are affected by leading edge suction. Also, simulation results show that the competence performance and convergence performance of the designed controller are obtained.

Tracking control of an underactuated ship by modified dynamic inversion

The tracking control problem of an underactuated ship is investigated. We intend to use the underactuated ship as an example to extend the traditional dynamic inversion control method to underactuated systems. The difficulty lies in the fact that the system has no relative degree, which prevents the application of standard dynamic inversion. Three modified dynamic inversion methods are proposed that are applicable to this system. The first is the well-known dynamic extension-based dynamic inversion (DEDI), which treats an input as a state and takes dynamic extension to achieve a relative degree. The second is virtual input-based dynamic inversion (VIDI), which treats a state as a virtual input to achieve a relative degree. The third is output redefinition-based dynamic inversion (ORDI), which selects a particular variable as a new output to achieve a relative degree. The three methods are generalizations of dynamic inversion control and remove some of its inherent limitations, making it applicable to a wide variety of underactuated systems. The effectiveness of the proposed methods is verified by numerical simulations.

Application of dynamic rod worth measurement in a VVER

Abstract Control rod worth measurement is very important in physical experiments before every cycle of nuclear plants. The traditional method is boron dilution method. DRWM (for Dynamic Rod Worth Measurement) (Chao et al., 2000) is an advanced method developed by Westinghouse and Electric Power Research Center. The main idea is to record the current signals from reactors, which is converted as reactivity by using inverse dynamic method. Besides, corrections are needed to get a good result. In China, an advanced reactivity meter made by China Institute of Atomic Energy is applied in a VVER. VVER is the abbreviation of Vodo-Vodyanoi Energetichesky Reactor in Russian. It is one kind of PWR using hexagonal fuel assembly developed by Russia. This paper gives the application of dynamic rod worth measurement in a VVER in Jiangsu Nuclear Plants. The correction coefficient calculations, experimental details and results would be introduced.

Control valve stiction compensation by dynamic inversion: a comparative study

PurposeThe purpose of this paper is to improve the performance of control loop suffering from control valve stiction. Control valve stiction is considered as of one of the main causes of oscillation in process variables, which require performing costly unplanned maintenance and process shutdown. An adaptive solution to handle valve stiction while maintaining safety and quality until next planned maintenance is highly desirable to save considerable cost and effort.Design/methodology/approachThis paper implements a new stiction compensation method built using adaptive inverse model techniques and intelligent control theories. Finite impulse response (FIR) model, which is known to be robust, as a compensator for stiction. The parameters of FIR model are tuned in an adaptive way using differential evolution (DE) technique. The performance of proposed method is compared with other two compensation techniques.FindingsThe new method showed excellent performance of the DE–FIR compensator compared to other dynamic inversion methods in terms of minimizing process variability, energy saving and valve stem aggressiveness.Research limitations/implicationsThe compensation ability for all compensators reduces with the increase of stiction severity, thus the over shoot case always shows the worst result. In future works, other optimization techniques will be explored to find the appropriate technique that can extend the FIR model size with smallest computation time that can improve the performance of the compensator in over shoot case. In addition, the estimation of the valve residual life based on the level of stiction and effort required by the controller should be considered.Originality/valueThe presented approach represents an original contribution to the literature. It performs stiction compensation without a need for a prior knowledge on the process or the valve models and guarantees a smooth control of the stem movement with a low control effort. The proposed approach differs from previous adaptive methods as it uses stable FIR models and DE to find the appropriate parameters of the inverse model and handle nonlinear behavior of stiction.

How is hip prosthesis and proximal femoral nail stability affected by lesser trochanter fractures: A comparative finite element analysis.

This study aims to evaluate the effects of lesser trochanter (LT) and iliopsoas tendon on implant stability by using finite element analysis (FEA). Effects of iliacus and psoas major muscles on hip joint was evaluated with inverse dynamics methods to calculate joint reaction and muscle forces. Intertrochanteric femur fracture was simulated according to AO (Arbeitsgemeinschaft für Osteosynthesefragen) 31A1 and 31A2 classifications in three-dimensional modelling software. Uncemented three-dimensional model of modular nail prosthesis combination was used in FEA. All analyses were performed with Ti6Al4V's 114 GPa elastic modulus value. Effects of LT on implant stability were evaluated with two different implant designs using the same femoral stems and four different femoral models, two of which with intact LT and two of which with fractured LT. Reaction forces of the hip joint decreased by 10% in the 0-40° hip flexion range. Maximum stress distribution for proximal femoral nail (PFN) model with fractured LT was 204.68 MPa at the distal locking screw on the interconnection point of PFN, while it was 335.35 MPa for the hip prosthesis with fractured LT. The direction of stress distribution for PFN model with fractured LT varied from medial to lateral and anterior to posterior. Maximum stress distribution for the hip prosthesis model with intact LT was 357.42 MPa, with direction of stress distribution from lateral to medial and posterior to anterior. Hip prosthesis models with intact or fractured LT were similar in terms of stress distribution and deformation values, while there were differences between PFN models with intact or fractured LT. Thus, intact LT was significant in PFN implant stability. Further clinical and experimental analyses are necessary on this topic.

The effect of increased shooting distance on energy flow in basketball jump shot

The aim of this study is to clarify the effect of shooting distance on energy flow in basketball jump shot. Ten male right-handed basketball players participated in this study, and three successful shots at three different distances (short condition, equating to a free-throw; long condition, equating to a three-point shot; and mid condition, equating to the mid-point of the short- and long-condition shots) were recorded using a motion capture system and force platforms. Kinetic variables of joints during shooting were analysed using inverse dynamics method. Our results showed that the joint work was not significantly different for short- and mid-condition shots; however, the amount of energy transferred from the torso to the shooting arm by the shoulder joint force increased significantly for the mid-condition shots ( as opposed to J/kg, ), whereas between the mid- and long-conditions, it was found that the joint work in the lower limbs increased significantly ( as opposed to J/kg, ). These results suggest that sufficient energy transfer from the lower limbs to the shoot arms is important to keep the motions of the shooting arms approximately constant when shooting from various distances.

Shoulder torques resulting from luggage handling tasks in non-inertial frames.

This paper reports on the torques developed in the shoulder joint experienced by occupants of moving vehicles during manual handling tasks. Handling heavy weights can cause musculoskeletal injuries, especially if handling is done with arms extended or at high levels. The aim of the study was to measure the longitudinal and lateral accelerations in a variety of passenger vehicles together with the postures of subjects lifting luggage onto storage shelves. This data enabled the application of inverse dynamics methods in a non-inertial reference frame to calculate the shoulder joint torques. The subjects lifted 3 pieces of luggage of masses of 5 kg, 10 kg and 14 kg onto shelving which were at heights of 1.2 m, 1.6 m and 1.8 m. The movement of subjects was measured using a 12 camera, 3-dimensional optical tracking system. The subjects stood on force plates to measure the ground reaction forces. Sixty-three trials were completed, although 9 trials were aborted because subjects felt unable to complete the task. It was found that the shoulder torques exceeded the levels recommend by the UK Health and Safety Executive for manual handling. A lift assistance device is suggested to reduce the shoulder torques required for luggage handling.

Influence of saddle setback on knee joint forces in cycling

Knee functional disorders are one of the most common lower extremity non-traumatic injuries reported by cyclists. Incorrect bicycle configuration may predispose cyclist to injury but the evidence of an effect of saddle setback on knee pain remains inconclusive. The aim of this study was to determine the effect of saddle setback on knee joint forces during pedalling using a musculoskeletal modelling approach. Ten cyclists were assessed under three saddle setback conditions (range of changes in saddle position ~6 cm) while pedalling at a steady power output of 200 W and cadence of 90 rpm. A cycling musculoskeletal model was developed and knee joint forces were estimated using an inverse dynamics method associated with a static optimisation procedure. Our results indicate that moving the saddle forwards was not associated with an increase of patellofemoral joint forces. On the contrary, the tibiofemoral mean and peak compression force were 14 and 15% higher in the Backward than in the Forward condition, respectively. The peak compression force was related to neither pedal force nor quadriceps muscle force but coincided with the eccentric contraction of knee flexor muscles. These findings should benefit bike fitting practitioners and coaches in the design of specific training/rehabilitation protocols.

Extended state observer based control for generic hypersonic vehicles with nonaffine-in-control character

This paper investigates the flight control problem of generic hypersonic vehicles subject to nonaffine-in-control character. Considering the large uncertainties and external disturbance, the disturbance observer based control strategy is incorporated in the control scheme. Firstly, an extended state observer is used to estimate the system states and the total disturbance. Then, based on the output of the extended state observer, we follow the backstepping design procedure. The dynamic inversion method is involved in the last step of backstepping to solve the nonaffine-in-control problem. The proposed control scheme ensures that the hypersonic vehicle tracks the command signal with almost no aerodynamic knowledge. Rigorous stability proof is given based on the separated time-scale structure of the extended state observer and the dynamic inversion method. At last, numerical simulations are presented in different conditions to demonstrate the effectiveness and good tracking performance of the proposed control scheme.

Full Dynamic Compound Inverse Method for seismic output-only element-level and input identification: Unitary formulation and extensive validation

Abstract The present work develops a unitary formulation of a novel deterministic output-only system identification and input estimation technique named Full Dynamic Compound Inverse Method (FDCIM) and outlines a systematic investigation on its consistent adoption within seismic engineering, by considering specific aspects of Signal Processing and producing a complete statistical evaluation. The achieved comprehensive FDCIM technique successfully estimates, all together: modal properties, element-level structural characteristics and earthquake input time history. Here, previous detached seminal contributions are first rejoined, in order to deal with various forms of structural viscous damping. Then, a wide database of ten selected real seismic excitations is taken into account to generate a set of synthetic earthquake-induced structural response signals, from a benchmark low-rise three-storey shear-type frame and from a realistic mid-rise ten-storey building. Such synthetic signals, possibly affected by noise of a controlled amount, are successfully processed via FDCIM and the achieved results demonstrate, as a first necessary validation condition, the consistency of the present identification algorithm toward potential Structural Health Monitoring purposes within the earthquake engineering range. Finally, a closing validation is proposed with the use of real earthquake-induced response signals, from an instrumented case study out of the CESMD database, with rather promising identification outcomes.

Designing instrumented walker to measure upper-extremity’s efforts: A case study

ABSTRACT The high prevalence of shoulder pain in using walkers in patients who have spinal cord injury (SCI). Also, the limited options available to economically measure grip forces in walkers, which drove the need to create one. This article describes a method to obtain upper-extremities’ forces and moments in a person with SCI by designing an appropriate instrumented walker. First, since the commercial multidirectional loadcells are too expensive, custom loadcells are fabricated. Ultimately, a complete gait analysis by means of VICON motion analysis and using inverse dynamic method has been held to measure upper-extremities’ efforts. The results for a person with SCI using a two-wheel walker in low and high heights and a basic walker show that there are higher shoulder and elbow flexion-extension moments and also higher shoulder forces in superior–inferior direction and higher elbow and wrist forces in anterior–posterior directions. The results are not much different in using two different types of walker. By using the proposed method, upper-extremities’ forces and moments were obtained and the results were compared to each other in using two different walkers.

Time-Suboptimal Satellite Formation Maneuvers Using Inverse Dynamics and Differential Evolution

This paper presents an open-loop planner for near-time-optimal maneuvers performed by satellite formations during proximity operations and reconfiguration maneuvers. Using a differential flatness parameterization, which is an inverse-dynamics method with a minimal set of independent functions, a new optimization technique based on the differential evolution is presented. The linearized dynamical model including the perturbation is taken into account. The differential flatness formulation is implemented to obtain the control policy and the full state as a function of the relative displacements in the local reference frame. The differential evolution algorithm with a local neighborhood, in which the risk of stopping at local minima is reduced, is employed. The technique is computationally efficient and evaluates near-optimal solutions characterized by approximated bang–bang control policies. Results are reported to evaluate the performances of the proposed technique, and a Monte Carlo simulation has been run to prove the efficiency of the planner over a variety of different scenarios. Moreover, the Chebyshev and the B-spline approximations are compared to establish that the latter approach guarantees better results than the former, in terms of maneuver time and computational effort.

Kinetic Analysis of Fingers During Aimed Throwing.

This study had two objectives: (a)revealing the difference in finger segments between the conventional and finger models during aimed throwing and (b)examining the central nervous system's timing control between the wrist torque and finger torque. Participants were seven baseball players. Finger kinetics was calculated by an inverse dynamics method. In the conventional model, wrist flexion torque was smaller than that in the finger model because of the error in ball position approximation. The maximal correlation coefficient between the wrist torque and finger torque was high (r = .85 ± .10), and the time lag at maximal correlation coefficient was small (t = 0.36 ± 3.02ms). The small timing delay between the wrist torque and finger torque greatly influenced ball trajectory. We conclude that, to stabilize release timing, the central nervous system synchronized the wrist torque and finger torque by feed-forward adjustments.