• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.4
• /
• pp.78-87
• /
• 1997

In machine tools, frictional force exists between the table and the guideways, and in ballscrews. In this paper, feed motor current measured by a hall sensor is used to calculate the motor torque. Some frictional phenomena are studied in feed drive systems, such as the relationship between feedrate and frictional torque, and chip cover effects on frictional torque. Considering frictional phenomena, the relation- ship between the feed froce and the feed motor current id obtained. Feed force can be well estimated by feed motor current measurement considering frictional behavior. The relationship between the cutting force and the feed motor current is slightly different between up milling and down milling due to the effect of y direc- tional cutting force on frictional torque.

• 제어로봇시스템학회:학술대회논문집
• /
• 2002.10a
• /
• pp.68.5-68
• /
• 2002

For the performance test of rechargeable electric tools, it is necessary to test under the same condition as the actual operation condition. They are necessary to control the load torque and to acquire the test data with a computer, and it should be convenient to fix the tool on the test equipment for rechargeable electric tools. It consists of torque loading parts, sensing parts and control software. Two hysteresis brakes, connected serially with flexible coupling, were applied to control the load for the test. The sensing part consists of a torque sensor, a rpm detector and a power analyzer. The torque and the rpm were measured in order to calculate the output of the rechargeable electric...

• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.978-980
• /
• 2000

Sensorless PMSM is much studied for the industrial applications and home appliances because, a mechanical sensor reduces reliability and increases cost. Two types of instantaneous torque controls are basically used for high performance variable-speed a.c. drive : vector control and direct torque control. This paper investigates speed sensorless control of PMSM using direct torque control. The switching of inverter is determined from SVPWM realizing the command voltage which is obtained by flux error and measured current without d-q transformation. The rotor speed is estimated through adaptive observer with feedback loop. The simulation and experimental results indicate good performances.

• Korean Journal of Applied Biomechanics
• /
• v.31 no.2
• /
• pp.140-147
• /
• 2021

Objective: The purpose of this study is to identify the mechanism of changes in maximum voluntary torque with the magnitude and duration of pre-activation torque during voluntary isometric knee extension. Method: 11 male subjects (age: 25.91±2.43 yrs., height: 173.12±3.51 cm, weight: 76.45±7.74 kg) participated in this study. The subjects were required to produce maximal voluntary isometric torque with a particular pre-activation torque condition. The properties of pre-activation torque consisted of the combinations of 1) three levels of magnitude, e.g., 32 Nm, 64 Nm, 96 Nm, and 2) two levels of duration, e.g., 1 sec, and 3 sec; thus, a total of six conditions were given to the subjects. The force and EMG data were measured using the force transducers and wireless EMG sensor, respectively. Results: The results showed that the maximum voluntary torque increased the most with relatively large and fast (96 Nm, 1 sec) pre-activation condition. Similarly, with relatively large and fast (96 Nm, 1 sec) preactivation, it was found that the integrated EMG (iEMG) of the agonist muscles increased, while no significant changes in the co-contraction of the antagonist muscles for the knee extension. Also, the effect of pre-activation conditions on the rate of torque development was not statistically significant. Conclusion: The current findings suggest that relatively larger in magnitude and shorter in duration as the properties of pre-activation lead to a larger magnitude of maximal voluntary torque, possibly due to the increased activity of the agonist muscles during knee extension.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.2 s.233
• /
• pp.311-317
• /
• 2005

NC controller parameters are fixed when the controller is combined with a machine. However, the characteristics of controller could be changed as it has being used by the machine or other environmental conditions. Ultimately, it results in tool positioning accuracy changing. The loading torque in servo motor also influences on the positioning accuracy. This study focus on a measuring and analysing method for verifying the angular positioning accuracy of NC servo motor. We used a high resolution A/D converter for acquiring analogue signal of rotary encoder in servo motor. Generating tool path by the combination of axial movements (X,Y,Z) is compared with the encoder signals with the servo motor torque. The current variation signal is also read from the servo motor power using a hall sensor and converted to the motor torque. The method of analysing proposed in this study will be used for determining the gains (tuning) of parameter in NC controller, when the controller is set up at a machine initially or the controller condition is changed during the work.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.3
• /
• pp.1048-1057
• /
• 2015

This paper proposes a sensorless speed control algorithm for parallel-connected dual Surface-mounted Permanent Magnet Synchronous Motors (SPMSMs) fed by a single inverter. For stable parallel operation of synchronous motors with a single inverter, each motor has to be constantly kept in the synchronization state regardless of load torque. If the master motor with the larger load is controlled, the synchronous state will be maintained. Therefore, detection of the master motor is essential. Conventionally, the master motor is determined by comparing the rotor position error from the relation between the back-EMF for torque angle and the flux position; consequently, the position sensor is deemed essential for finding the rotor position. The parallel sensorless speed control method proposed in this paper uses no position sensor, instead it compares the flux-axis current from the connection between the back-EMF for torque angle and current in unbalanced load conditions. The results of simulation and experiment conducted verify the efficacy of the proposed method.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.7
• /
• pp.615-620
• /
• 2015

DOB (Disturbance Observer) is an useful control method for estimating the disturbance applied to dynamic systems. Disturbance observer can be used to implement a robust control system to generate a control input for rejecting the disturbance, and it can be also used to estimate the disturbance to obtain information. The system that uses disturbance estimation is investigated for high performance control such as automatic door systems, walking robot and electric power steering system in vehicles. In this paper, a novel disturbance observer which is called disturbance and current observer for estimating load torque in the motor system is proposed. The difference between the DOB for disturbance rejection and DCOB is mathematically verified. Current and angular velocity are required for estimating the load torque of the motor in DOB. However, the DCOB can estimate load torque and current without current sensor. DCOB is designed based on modeling of the motor system. Appropriate Q-filter is selected and the applicability of DCOB is verified by simulation. The estimated disturbance and current of the electric motor can be verified without current sensor, as experiments of the actual motor system.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.768-771
• /
• 1997

Geometric probing addresses the problem of determining geometric aspects of a structure from the mathematics and results of a physical measuring device such as a probe. This paper presents a new algorithm to recognize the shape of an unknown object by using a robot hand with a force and torque sensor. The new algorithm is called S.E.P.(Shape Exploration Procedure) which finds the global shape of an unknown object. The proposed method is composed of three major parts, finding contact informations such as contact point, calculation of shape information such as curvature, and expression of global shape from these informations. Comparing with the conventional approaches, the advantages of the proposed method are explained and verified by conducting experiments with a 3-dof SCARA robot.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1778-1781
• /
• 1997

The coke oven plant on a steel works has not, in the past, been regarded as a prime user of modern instrument technology. The reason for this perception may be due to the fact that the basic design of the coke battery has been changed little over the years. The recording and analysis of oven pushing force on a routine basis is seen as a means of monitoring plant operation. A torque sensor is set up at the shaft of the rotor for measuring pushing force. Pushing force data which is communicated form torque sensor to staor by telemetry method are shown on MMI(Man-Machine Interface) screen and stored in the database automatically. Perhaps the most important feature is that is allows a problem oven to be identified at an early stage and for corrective action to be taken before it develops into a refusal to push. In this way the mechanical loads imposed on the battery structlure can be held to a necessary minimum, so helping to prolong its service life.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.2 s.95
• /
• pp.130-137
• /
• 1999

In this paper we propose a method of determining the local curvature of a three dimensional convex object using the force and torque information obtained from the active touch of a robot hand. A technique for estimating two dimensional curvature of a convex object are introduced and the way of computing the three dimensional curvature from the two dimensional vurvatures is presented. Also, we develop an experimental system consisting of a finger and verify the effectiveness of the proposed method experimentally.