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Atos directional proportional valves: the evolution of industrial control systems

Alternated p/Q control technology to boost industrial processes


The new generation of directional proportional valves from Atos represents a significant evolution in the electro-hydraulic sector; Among the key innovations is the integration of alternated p/Q control technology, which brings advanced and sophisticated control algorithm, strong machine architecture simplification and easy programmability thanks to the powerful digital interface.
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Alternated p/Q control introduction p/Q control configurations The Atos difference: unmatched flexibility and customization Compatibility and integration with directional proportional valves & pumps Contact Us

Alternated p/Q control introduction

Speed, Force, Direction are the key control parameters in most industrial machinery that, thanks to automation, bring to life the sequence of commands and operations that define the machining process.

Taking a vertical press as an example, these parameters are traditionally controlled using three separate devices: a solenoid valve for on/off directional control, a flow control valve, and a pressure reducing valve. This is undoubtedly a simple and effective solution, however, with alternated p/Q controls, we can simplify the setup by performing all three functions with a single directional proportional valve.

In fact, the “alternating p/Q control” allows for the regulation of direction, flow, and pressure with a single digital valve, which in turn controls the direction, speed, and force of any hydraulic axis, depending on the hydraulic condition of the actuator. The term “alternating” means that the pressure “p” and flow “Q” parameters cannot be controlled simultaneously, with one taking priority over the other.

This aspect represents a significant simplification of the machine architecture, permitting to continuouslymodulate the p and Q parameters with high dynamics and accuracy, facilitated by programming through USB/Bluetooth connection with a powerful and intuitive graphical interface in our software and mobile App.

The alternated p/Q control features robust and versatile algorithms, honed over years of experience across a multitude of applications; this category of devices represents one of the most powerful and advanced products in Atos range.

p/Q control configurations

The alternated p/Q control adds the closed loop control of pressure-force to the spool position control of directional proportional valves, or swash plate control for axial piston pumps.

There are three configurations for Atos alternated p/Q control:

  • Single pressure transducer (SP): it performs the closed loop pressure controls on a single user line of the hydraulic circuit and it has to be interfaced to one pressure transducer.
    This option is present in axial piston pumps, servo pumps and directional proportional valves. Thanks to its simplicity, it is widespread in many industrial applications, e.g. plastic injection and hydraulic presses.

  • Double pressure transducer (SF): the most common and widely used configuration regulates the actual force exerted by the actuator by reading pressure transducers installed on both chambers of the actuator, calculating the force in relation to the actuator pushing areas.
    This system is ideal solution for applications requiring precise force control, which can be applied in both directions of actuator movement. It is often combined with closed-loop position controls for hydraulic axes.

  • Load cell (SL): the most effective configuration for controlling the actual force exerted by the hydraulic actuator, thanks to the force feedback signal read via a load cell installed directly on the cylinder rod.
    This solution makes force control independent of mechanical friction and is typically used in high-precision applications, such as test benches, measuring systems or structural testing systems.

<br />Alternated p/Q controls configurations

Alternated p/Q controls configurations
Regardless of the selected configuration, which can be modified at any time via dedicated programming software, the p/Q control autonomously switches from flow to pressure-force control and vice versa, when a threshold defined by the reference signal in pressure is reached, always ensuring a smooth transition to avoid shocks, overshoots or vibrations.
In the practical application of a hydraulic press, the p/Q control will switch from speed to closed loop force regulation in the instant when the cylinder piston comes in contact with a load or the piece to be worked.

The Atos difference: unmatched flexibility and customization

Four different pressure/force PID parameters sets, dynamically selectable within the machine cycle via Fieldbus or digital input, allow for extremely high precision and reliability in control, even when using varying load conditions or oil volumes.
The possibility to select between different switching algorithms for the two logics “p” and “Q”, plus the adjusting of PID selection to optimize the switching point between the two logics to ensure a smooth changeover, allows alternated p/Q control to improve the overall pressure-force control response of hydraulic systems.

Additionally, the following control options are available to further customize the alternating logic to specific application:
  • Push, pressure/force control active only in the forward direction
  • Pull, pressure/force control active only in the backward direction
  • Push and Pull, pressure/force control active in both actuator directions
These several different options make Atos alternated p/Q controls robust and versatile, providing a high degree of freedom to the end user during driver configuration, and thus capable of perfectly meeting system requirements, even the most challenging ones.

Compatibility and integration with directional proportional valves & pumps

The alternated p/Q controls is available in combination with highperformance proportional valves or servoproportional directionals, whether direct or pilot-operated. It can also be paired with the most sophisticated axis controls, variable displacement piston pumps and servo-pump systems.
These controls guarantee unmatched accuracy and reduced machine cycle times, even in the most complex, harsh and selective industrial environments, thanks to the numerous options offered by Atos range:
  • On-board driver execution: refers to the integration of electronic drivers directly onto high-performance proportional valves or servoproportional directionals, all in one solution.
  • Off-board driver execution: the electronic driver is commonly installed in a cabinet through a DIN rail system, which provides an organized and safe environment for electronic components.
  • Ex-proof execution: specifically designed for hazardous environments where explosive gases, dust or chemicals are present.
  • Fieldbus interfaces: CANopen, PROFIBUS DP, EtherCAT, POWERLINK, EtherNet/IP and PROFINET.
  • Functional safety certification - options /U, /K: conforming to Machine Directive 2006/42/EC and certified by TÜV according ISO EN 13849 up to category 4, PL e and IEC 61508 up to SIL2 / SIL3.
Industrial and ex-proof valves with<br />alternated p/Q control Industrial and ex-proof valves with
alternated p/Q control

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Source: PR17
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