This section offers an overview and basic knowledge on motion control in an easy-to-understand way.
Motion control means “to control movement.” One distinctive example is positioning control by various motors. By giving electronic energy to a motor, a motor operates and converts it to motional energy. This technology has a key role in machining tools, robotic control, semiconductor manufacturing equipments, injection molding machines, and digital home electronics inspection machines. The equipment investment in this field is largely growing these years.
Rotation control of conveyors
Axis control of multi-axis robot
Positioning control of rotating table
Positioning control of XY table
Motion control board mounts functions to output pulse train at designated pulse number or frequency. It can automatically output control pulse according to motion parameters such as target position, velocity, acceleration and deceleration rate, etc. It has various limit input functions for positioning control. Motor driver controls motor itself. Motion control board outputs pulse signal for the motor driver unit and controls motor. It is connected with pulse input type stepping motors or servo motors.
See all motion control devices
A motor driver unit is a control unit to drive stepping motors and/or servo motors. Setting/acquiring control signals for this driver unit enables motor control.
Stepping motor is capable of high-precision positioning. By synchronizing to the input pulse, it rotates by a certain angle in stepwise. Stepping motor is operable for high-precision positioning which does not require rotation amount detection because it accurately rotates to the input pulse. General resolution is 1 step (1 pulse) = 1.8°, 0.72°, and 0.36°.
Step angle is an angle that motor rotates when 1 pulse is input on motor driver by stepping motor. 1 step (1 pulse) = 1.8°, 0.72°, and 0.36° is common angle. Pulse number assigns rotation quantity and pulse frequency assigns rotation velocity.
Example) What is necessary pulse number to move carrier for 50 mm when stepping angle is 0.72°?
Rotation velocity of stepping motor is exactly proportional to pulse signal velocity. Relation between rotation velocity and pulse signal is set up by the following formula. Pulse number assigns rotation quantity and pulse frequency assigns rotation velocity.
Motor rotation velocity (r/min) = step angle (°) / 360° × pulse velocity (frequency: Hz) × 60
Losing steps refers to when a stepping motor cannot rotate in sync with pulses because of a rapid change in velocity (acceleration and deceleration) or an excessive load, resulting in stoppage or offset positioning. Recent stepping motor has a structure that does not generate losing steps.
Servo motor has two types; AC servo motor and DC servo motor. Servo motors are widely used on machining tools and industrial robots at manufacturing factories. Servo motor has encoder to detect rotation angle, and high-precision positioning is done on closed loop. Our motion control boards are applicable to pulse input type servo motors.
Our motion control board mounts counter function for feedback control. By connecting to incremental encoder (UP/DOWN motion), high-precision feedback control is operable. Feedback control itself requires programming. Input circuit is compatible with two-phase (A/B phase) and single-phase (UP/DOWN). It can be used with encoders compatible with differential output, TTL level output, and open collector output.
Our motion control board has following output types compatible to pulse train input type motor drivers.
Control type by emitting two independent pulse signals indicates forward (CW) and backward (CCW). CW (clockwise) indicates rotation to the right, and CCW (counter clockwise) indicates rotation to the left.
Control by one pulse signal controlling travel distance and velocity, and a signal deciding rotation direction.
Outputs OUT (forward pulse output) signal and DIR (delay pulse output) signal. In case the phase of DIR and OUT is +90° different, it moves (rotates) to forward (Clockwise). In case the phase of DIR and OUT is -90° different, it moves (rotates) to backward (Counter Clockwise).
Our motion control boards are capable of synchronizing control of inter-multi-axis synchronizing start/stop. By connecting to designated synchronizing control cable, maximum of 16 frames (128 axes) can be controlled synchronizing. For 8-axis board, grouping by 4-axis is possible.
A function to detect stop, deceleration point, and origin of motor (carrier). It is capable of high-precision positioning control.
A driver unit can transmit alarm code at the same time as alarm signal occurrence. An alarm code indicates cause of alarm occurrence. By receiving alarm code on application, it can output (emergency) operation process according to each alarm code on the screen. Operators can conduct designated (emergency) operation quickly.
Driver unit of servo motor and stepping motor needs to stop its motor to protect itself from overload, over voltage and over heat. In those cases, driver unit transmits alarm signal to the board (application). By receiving alarm signal, it stops movement of axis on synchronizing setting as well. When application receives alarm signal, the system needs to be disconnected for process and alarm signal needs to be canceled. In this case, it transmits alarm clear signal.
Utilize hold off signal to sustain the hold status at positioning of stepping motor. (Automatically) turn the hold to OFF (hold off) inside board during motor movement, turn the hold ON (hold on) when motor stops.
Servo motor has deviation counter inside driver unit, and it functions to count deviation between input pulse and feedback pulse. When pulse is input into driver, counter accumulates pulse (accumulated error pulse). When motor rotates, accumulated error pulse is decreased by feedback signal for positioning control so that accumulated error pulse ends in 0. In case of origin return motion, motor stops immediately at the origin detection, deviation could accumulate in the counter, and accumulated error pulse could remain. By setting deviation counter clear signal into driver unit, origin return completes.
PTP motion means movement between one point to the other (Point To Point). It is used for simple positioning control. Our motion control board is capable of changing stop position at desired timing even during motion. The figure on the right indicates the case of changing the target position to further during acceleration / constant velocity movement. For example, during movement from start point to the 3000-pulse point, the point can be changed to the 5000-pulse point without halting.
JOG motion is a transfer motion without traveling distance designation. It is used for manual motor positioning. The motor keeps operating until ±LIM signal input or stop order is given. The velocity and acceleration and deceleration time can be changed at any desired timing during operation.
ORG (origin return) motion is a movement for shifting motor to the origin point. We are capable of unique origin return movement as follows. By origin return motion setting, ORG motion is set to motion type, and when movement starts, the driver automatically control until origin return completes.
Thus, origin return motion is easy without a need for creating origin return logics.
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Outputs pulse at the constant velocity (frequency). An equipment moves at the constant velocity. Sudden velocity change occurs at the start-up and stop.
Movement to absorb shocks at the start-up and stop by accelerating / decelerating the velocity at the constant rate at the start-up and stop. It is also called as trapezoidal velocity control.
Velocity control method further reduces the abrupt shocks on linear acceleration and deceleration movement. By reducing acceleration rate at the start-up and stop period of acceleration and deceleration, the shocks at the movement start-up and stop are diminished.
Three multi-axis control types to move from start point to target point when controlling more than 2 axes.
First move the X-axis to point (Xt), then move the Y-axis to point (Yt).
Coordinate control of both the X-axis and the Y-axis, and move the to points (Xt, Yt) so that the trajectory follows a linear profile.
Assign central coordinate of circular and target point on the circular. While synchronizing control both X-axis and Y-axis, move the points to (Xt, Yt) so that the trajectory follows profile as programmed.
Our motion control boards deal motor movement parameter groups such as travel distance, travel velocity, acceleration and deceleration rate as one frame, and download consecutive multiple frames into onboard memory and then execute. This is a great advantage that did not exist before.
For fixed pattern motion control, high velocity control without load on CPU of PC is possible even under complicated control.
The idle time of switching to next motion is within 1μsec since continuous switching of each frame is operated on hardware.
Thus, highly efficient systems can be constructed. Continuous multi-axis interpolation control is possible by combining various interpolation controls.
Our motion control board mounts 7 general input (control signal input) and 3 general output (control signal output) per axis.
Automatically controls on board side by various I/O signals IN1-IN6, OUT1-OUT3.