Joint TDOA and AOA location algorithm

For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.

Arm motion control model based on central pattern generator

According to the theory of Matsuoka neural oscillators and with the con- sideration of the fact that the human upper arm mainly consists of six muscles, a new kind of central pattern generator （CPG） neural network consisting of six neurons is pro- posed to regulate the contraction of the upper arm muscles. To verify effectiveness of the proposed CPG network, an arm motion control model based on the CPG is established. By adjusting the CPG parameters, we obtain the neural responses of the network, the angles of joint and hand of the model with MATLAB. The simulation results agree with the results of crank rotation experiments designed by Ohta et al., showing that the arm motion control model based on a CPG network is reasonable and effective.

Development of agricultural bionic mechanisms:Investigation of the effects of joint angle and pressure on the stability of goats moving on sloping lands

The use of small-scale agricultural machinery becomes prevalent as it provides the stability of agricultural machinery research ideas.To lay the theoretical foundation for the research and design of agriculture walking mechanism,the Phantom Camera Control software was used to measure the anterior and posterior joint angle of a goat walking on different slopes.Foot pressure was measured by the film pressure sensor.The result of joint motion sequence,range of motion,and change of range showed that the fitting degree of the measured value was accurate.As the goat walking speed increased,the level of the hind limb angle changed to ensure itself stability.When the goat is walking,the forelimbs bear more weight than the hind limbs due to the different static and physiological structures of the front and rear legs.The key parameters of gait on different slopes were analyzed.The curve of angle change of legs was measured and analyzed when the goat is walking in slope.The results showed that,with the increase of the slope gradient,the anterior hip angle ranges from 83.3°to 117.1°,the posterior hip angle ranges at 120.3°-173.1°,the left knee angle ranges from 91.3°to 170.1°,the right knee angle is roughly the same as its range of variation.When the slope increased,the pressure change of left hind foot was consistent with that of the right anterior foot,and the pressure change of right hind foot was consistent with that of the left anterior foot.This demonstrated the theory of diagonal gait.Meanwhile,with the change of the slope,the plantar pressure of the limbs changes periodically.The research results verified the rationality of the four-legged bionic mechanism under various parameters,which can provide a theoretical basis for the design of agricultural walking mechanism to adapt different slopes in the hilly and mountainous areas.

Effects of a 12-week online Tai Chi intervention on gait and postural stability in individuals with Parkinson’s disease

Parkinson's disease(PD)affects gait and postural stability.Tai Chi(TC)is recommended for PD for management of the condition,however biomechanical understanding to its effects on gait and postural stability is limited.This study aimed to examine the effects of an online 12-week biomechanical-based TC intervention on gait and posture in people with PD.Fifteen individuals in early-stage PD were recruited(Hoehn&Yahr stages 1-2).The TC intervention program was 60min session,three times weekly for 12 weeks.The pre-and post-intervention test in obstacle crossing,timed-up-and-go(TUG)test,and single leg standing(SLS)with eyes open(EO)and closed(EC)were conducted.Gait speed,crossing stride length,clearance height of the heel and toe,anterior-posterior(AP)and medial-lateral(ML)displacement and velocity of the center of mass(COM)and separation of the COM-center of pressure(COP)were analyzed.The participants significantly improved their pre-vs.post-TC intervention performance on TUG test(p=0.002).During obstacle crossing,the participants significantly increased crossing stride length of the trailing foot,increased AP COM displacement and decreased ML COM-COP separation(p<0.05);the maximal dorsiflexion angle of the leading limb significantly increased and maximal plantarflexion angle of the trailing limb significantly decreased(p<0.05).A 12-week biomechanical-based online TC training was effective towards improvement of gait and postural stability among people in the early-stage of PD.The TC program and online training could be applied for management of PD.

A computer vision-approach for activity recognition and residential monitoring of elderly people

In this study,we explore a human activity recognition(HAR)system using computer vision for assisted living systems(ALS).Most existing HAR systems are implemented using wired or wireless sensor networks.These systems have limitations such as cost,power issues,weight,and the inability of the elderly to wear and carry them comfortably.These issues could be overcome by a computer vision based HAR system.But such systems require a highly memory-consuming image dataset.Training such a dataset takes a long time.The proposed computervision-based system overcomes the shortcomings of existing systems.The authors have used key-joint angles,distances between the key joints,and slopes between the key joints to create a numerical dataset instead of an image dataset.All these parameters in the dataset are recorded via real-time event simulation.The data set has 780,000 calculated feature values from 20,000 images.This dataset is used to train and detect five different human postures.These are sitting,standing,walking,lying,and falling.The implementation encompasses four distinct algorithms:the decision tree(DT),random forest(RF),support vector machine(SVM),and an ensemble approach.Remarkably,the ensemble technique exhibited exceptional performance metrics with 99%accuracy,98%precision,97%recall,and an F1 score of 99%.

Effects of body mass and sex on kinematics and kinetics of the lower extremity during stair ascent and descent in older adults

The effects of body mass and sex on lower limb biomechanics during ascent and descent were examined in participants aged 50 to 75 with normal weight(n=19),overweight(n=18),and obese(n=8).Peak joint angles and joint moment of the lower limb were analyzed with the VICON motion analysis system.Results from multivariate analysis of variance showed that during descent,the overweight participants had significantly higher knee extensor moment(0.98±0.30 N·m/kg^(-1))than the normal-weight participants(0.70±0.29 N·m/kg^(-1)).The obese group had significantly higher ankle abductor moment(0.21±0.11 N·m/kg^(-1))than the normal weight(0.12±0.08 N·m/kg^(-1))and overweight groups(0.09±0.06 N·m/kg^(-1)).During ascent,the obese participants had significant higher hip flexor moment(0.42±0.20 N·m/kg^(-1))than overweight participants(0.22±0.17 N·m/kg^(-1)).Significant sex differences were found in knee extension angles(4.2±3.4℃vs 7.0±3.3℃)during descent,plantar flexion angles during ascent(23.7±5.3℃vs 15.6±3.7℃)and descent(29.9±5.0℃vs 22.1±7.9℃),and ankle adduction angles(6.8±4.8℃vs 2.5±2.5℃)during ascent.It is concluded that body mass has significant impact on joint loading of lower limbs during stair walking.Being overweight and obese increased hip joint loading during ascent,and knee and ankle joint loading during descent in older adults.Sex difference in joint kinematics was presented during stair walking regardless of the body mass.

Biomechanics analysis of seven Tai Chi movements

This study examined the maximum joint angles and moments,and electromyography(EMG)activity of the lower limbs in an experienced Tai Chi(TC)practitioner in performing four dynamic(Repulse Monkey,Wave-hand in Clouds,Brush Knee Twist Step,and Lateral Forward Step)and three static TC movements(Starting Form,Hero Touch Sky,and Push Hand Back)and compared them with the measures from walking.Integrated EMG(iEMG)and peak EMG of the rectus femoris,adductor longus,tibialis anterior,semitendinosus,erector spinae,gluteus medius,tensor fasciae latae,medial and lateral gastrocnemius muscles were analyzed.One-way analysis of variance showed that compared with walking,TC presented 1)significantly larger hip flexion(71.4°vs.42.2°)and abduction angles(11.9°vs.5.3°),smaller knee flexion(45.2°vs.71.1°)and abduction angles(13.0°vs.27.7°),larger ankle dorsiflexion(41.4°vs.11.3°)and abduction angles(8.8°vs.7.2°);2)hip flexion moment and knee flexion and abduction moment were significantly larger.Ankle dorsiflexion moment were significantly smaller,whereas ankle abduction moment was significantly larger in two TC movements;and 3)the EMG activity of the muscles in TC varied from 10%to 610%of walking.The knee extensors,hip adductors and abductors had significantly higher peak EMG(430%±40%,240%±30%,and 320%±90%)and iEMG values(610%±30%,311%±30%,and 1.4%±20%),respectively.The findings suggested that these TC movements could be a good option for the improvement of muscle strength and range of motion of the lower limbs.

Nonlinear Dynamics of Torsional Vibration for Rolling Mill′s Main Drive System Under Parametric Excitation

The jointed shaft in the drivelines of the rolling mill, with its angle continuously varying in the production, has obvious impact on the stability of the main drive system. Considering the effect caused by the joint angle and friction force of roller gap, the nonlinear vibration model of the main drive system which contains parametric excitation stiffness and nonlinear friction damping was established. The amplitude-frequency characteristic equation and bifurcation response equation were obtained by using the method of multiple scales. Depending on the bifurcation response equation, the transition set and the topology structure of bifurcation curve of the system were obtained by using the singularity theory. The transition set can separate the system into seven areas, which has different bifurcation forms respectively. By taking the 1 780 rolling mill of Chengde Steel Co for example, the simulation and analysis were performed. The amplitude-frequency curves under different joint angles, damping coefficients, and nonlinear stiffness were given. The variations of these parameters have strong influences on the stability of electromechanical resonances and the characteristic of the response curves. The best angle of the jointed shaft is 4.761 3° in this rolling mill.

Kinematics of hip,knee,ankle of the young and elderly Chinese people during kneeling activity

Objective:The purpose of this study was to measure the kinematics of the lower limbs of Chinese people during normal kneeling activity,as such data could be valuable in designing joint prosthesis and arthroplasty that meet the needs of Chinese citizens' daily activities.Methods:Thirty young and twenty elderly Chinese participants with no personal history of joint diseases were recruited,and matched by age(average age:23.8 years for the young group,60.8 years for the elderly group).Each participant performed six trials during which three-dimensional(3D) kinematics data were collected and the means of the 3D angles of the ankle,knee,and hip joints of two groups were calculated.Results:There were no obvious differences between the two groups in the knee and ankle joints.The mean range of knee flexion was 139.6° for the young group and 140.9° for the elderly group.The mean range of ankle flexion was 35.7° for the young group and 37.6° for the elderly group.The maximal eccentric flexion at the hip joint was 67.5° for the young group compared to 100.5° for the elderly group.Conclusions:The elderly uses more hip flexion angles than the young when assuming the kneeling posture.The ranges of motion obtained during kneeling activity are greater than the reported mean ranges of motion achieved following joint arthroplasty.The data could be valuable in establishing criteria for lower limb prosthetics and rehabilitation protocol for the Chinese population.

Regional neuromuscular regulation within rectus femoris muscle following three-month limb-loaded walking in older adults

Limb-loaded walking using ankle weights has been widely applied to increase exercise intensity in older adults.Examining changes in the activation pattern between proximal(RFP)and distal(RFD)regions of the rectus femoris(RF)muscle is key to clarifying gait deficits in older adults.The aim of this study was to determine regional neuromuscular regulation within the RF muscle following three-month limb-loaded walking in older adults.The study participants were 22 healthy older adults(696.3 years)who walked at least 160 min per month.Surface electromyography(EMG)and motion capture were used to measure the neuromuscular activities of RFP and RFD and generate kinematic data on the left lower extremity on walking for 240 s at the preferred gait speed on a treadmill at pre-and post-intervention,respectively.Averaged rectified values(ARV)of RFP and RFD were normalized by maximum values of ARV during a gait cycle within ten consecutive gait cycles.Normalized ARV of RFP was greater than RFD at 30%–40%and 70%–90%of the gait cycle and hip joint flexion at 0%–100%,and the walking speed and swing timing at post-were greater than at pre-intervention(p<0.05).No significant differences were noted in the RFP to RFD activity ratio(RFP/RFD ratio)between pre-and post-intervention,and there was no correlation between the RFP activity level and hip flexion angle in the swing phase(p>0.05).The activity of RFP compared with RFD and hip joint flexion were increased following limb-loaded walking intervention in older adults.