The pulse signals from the optical magnetic pole sensor and optical encoder are received by encoder interface circuits on the gate array. After signal processing there, they are counted by an up/down counter in the microcomputer to compute the pen position and motor speed. Command signals for motor speed and commutation timing are then applied to the PWM** circuits according to the control algorithm, and the resulting pulse signals control the motor driver circuits that handle coil current commutation.
This servo system uses a new 2-stage control algorithm. In the first stage of positioning a nonlinear control algorithm called "Bang-Bang" is used for fast positioning. This has the shortcoming that variations in the mechanical parameters near the target make it prone to limit cycling, hampering fine positioning. The 2-stage algorithm overcomes this problem by switching near the target value to PID control, which is stable even at high positioning accuracy.
The combination of this 2-stage control algorithm with the high torque gained from the high-performance rotor magnet has increased the pen speed and frequency response by a factor of two compared with earlier Yokogawa products.
* ASIC: Application Specific IC ** PWM: Pulse Width Modulation

The LR Series recorders feature new techniques in the recording pens and platen, too. The disposable felt pens used on earlier models have been made smaller, lighter and longer-life by integrating the ink reservoir with the pen arm and expanding the ink capacity. This has doubled the recording life of our earlier pens.
The LR12000E recorder, for example, employs slimmer pen arms and wider ink reservoirs, enabling clear viewing even to the twelfth pen. This model has an ink storage capacity as large as that of the recording pens of other LR Series recorders, achieving high visibility, reduced weight and longer service life.

Conventional recorders also suffer from faint or broken traces at high writing speed (the vector sum of the pen speed and chart feed rate), and blotting and tearing of the paper at slow speeds.
For the LR Series, therefore, new inks were specially developed for high- and low-speed recording, and one of three pen types can be selected to suit the writing speed, greatly reducing the risk of blotches and paper tears. Another improvement is a slot in the platen, which solves the problem of low-speed ink blotting along the folds (lines of perforations) in the chart.