Semi-Active Suspensions - Noise, Vibration & Harshness Division | Parker US
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Suspension systems in today’s industrial equipment are evolving. Traditional passive spring and damper systems react to load inputs from the wheels and body, and exhibit relatively constant spring rates and damping forces regardless of the road and load conditions. In contrast, adaptive suspension systems continuously alter their suspension settings in real time to suit different driving or road surface conditions providing improved dynamic stability.

Advanced Suspension Systems

Heavy machinery operators spend a lot of their time in harsh and unpleasant vibration environments. Unlike passive suspension systems, Parker Lord Advanced Suspension Systems use patented Magneto-Rheological (MR) Technology to control and optimize vehicle suspension stability in real time. Our products provide superior vibration isolation with greatly enhanced shock control (hitting end stops), while continuing to provide protection against roll and pitch motions. Enhanced comfort and safety conditions contribute to improved driver responsiveness and efficiency.

 

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Magneto-Rheological Fluids

Magneto-Rheological (MR) Fluids consist of magnetic (typically iron) particles in a carrier fluid. In the presence of a magnetic field, the micron-sized particles link (see Figure 1 on the left, below) and change the fluid to a semi-solid in milliseconds.

 

When the magnetic field is removed, the fluid just as quickly reverts back to its natural free-flowing state (see the image on the left). Furthermore, the degree to which the fluid changes to a semi-solid is proportional to the strength of the magnetic field, giving the fluid infinite controllability and precision.

 

Our patented MR fluids exhibit fast response time, high dynamic yield stress, low plastic viscosity, broad operational temperature range, resistance to settling, easy remixing, and excellent wear and abrasion resistance.

 

 

 

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MR fluids consist of magnetic (typically iron) particles in a carrier fluid. In the presence of a magnetic field,  the micron-sized particles link and change the fluid to a semi-solid in milliseconds. When the magnetic field is removed, the fluid just as quickly reverts back to its natural free-flowing state. 

 

 

 

 

 

 

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MR fluids can be used in shear mode, with the fluid flowing between two surfaces (as in our SbW Tactile Feedback Device) or in a valve mode with fluid flowing through an orifice (as in a damper), which move relative to each other. In the absence of a magnetic field applied across the gap the fluid occupies, the fluid flows freely or allows free movement. Upon application of a magnetic field, the particles align like chains with the direction of the field.

The formation of these particle chains restricts the movement of the fluid within the gap since the fluid's yield strength is increased. Altering the inter-particle attraction by increasing or decreasing the strength of the field permits continuous control of the fluid's rheological properties and hence the damping or clutch or braking force.

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Adaptive suspension systems rely on quick detection of a disturbance and precise control of the damper for optimal suspension performance. Our control systems leverage a network of sensors that continuously monitor the driving situation in a vehicle and send data to the control unit via the CAN bus.

The control unit interprets these signals and regulates electrical current to the damper using sophisticated proprietary control algorithms. This process occurs continually thousands of times per second during vehicle operation to ensure the ideal suspension characteristics for the specific driving condition.

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Typical performance characteristics of various suspension technologies using a force-velocity curve. The speed at which MR technology changes damper forces enables more use of the damper stroke to control motion, improving the ride and handling for the operator.

Parker Lord has spent decades developing proprietary control algorithms that optimize the unique capabilities of MR Fluid technology.

 

 

How Does an MR Damper Work?

Similar to passive hydraulic dampers, an MR damper consists of a fluid that moves between different chambers via small orifices in the piston, converting "shock" energy into heat (see Figure 3).

 

However in an MR damper, an electrical circuit is introduced in the piston assembly. As electrical current is supplied to the damper, a coil inside the piston creates a magnetic field and instantaneously changes the properties of the MR Fluid in the piston (see Figure 4). Consequently, the resistance of the damper can be continuously changed in real time by modulating electrical current to the damper.

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Benefits of MR Seat Suspension System

Customized controllable damping significantly improves vehicle ride comfort, handling and safety.

  • Improved driver responsiveness, efficiency and pleasure
  • Reduced operator fatigue and risk of injury
  • Improved vehicle stability for safe maneuverability at higher speeds
  • Easily integrated with other vehicle electronic systems (braking, steering) to enable sophisticated vehicle dynamic control capability
  • Fail-safe (becomes a passive damper) or fail-firm (becomes rigid) design options if electrical power is lost
  • Better protection for cargo or goods

Simple electro-mechanical design is easy to integrate, improves reliability and reduces total cost.

  • No additional packaging space required versus conventional passive dampers
  • No maintenance required
  • Reduced wear on suspension and drivetrain components
  • Low power requirements (typically less than 5A)
  • Broad operating temperature range (-40°C to 120°C)
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