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AMBULANCE KIT  |
The Ambulance Kits, based on the CREUAT technology, is the simplest and cost effective possible hydropneumatic system devised to control the vehicle roll movements. Without sensors or actuators, it reacts instantaneously to wheel movements. It is designed to separate the dynamic response to each movement of the vehicle body such as roll and vertical movement appropriately for the vehicle distinct inertias. |
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OPTIONS |
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ELK TEST comparison |
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Conventional system |
Roll Control System |
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1 ROAD ELEVATION comparison |
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Conventional system |
Roll Control System |
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4 ROAD ELEVATIONS comparison |
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Conventional system |
Roll Control System |
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SIMULATIONS |
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Round about |
Road elevation |
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Conventional System |
Roll Control System |
Conventional System |
Roll Control System |
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ROLL CONTROL System (Top) 
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The ROLL CONTROL System, based on the CREUAT technology, is the simplest and cost effective possible hydropneumatic system devised to control the vehicle roll movements. Without sensors or actuators, it reacts instantaneously to wheel movements. It is designed to separate the dynamic response to each movement of the vehicle body such as roll and vertical movement appropriately for the vehicle distinct inertias. |
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The ROLL CONTROL System allows the specific configuration for the vertical and roll movements, providing better stability without impairing the comfort. It allows a great deal of optimization of the suspension settings for handling and stability well beyond the possibilities of a conventional or even active suspension system The ROLL CONTROL System interconnects the two wheel movements through a damper unit. It provides both static and dynamic additional roll stiffness. As explained above the ROLL CONTROL System offers the possibility of setting different springs rates and different damping rates for each modal movement. A typical case would set soft vertical rates to increase roll damping adjusting it for the body inertia. The examples below shows the parameters chosen for a particular application:
Softer vertical rates keep good comfort level. The different damping to roll and vertical movements are implemented in the hydraulic circuits include restrictors that act as selective dampers, so each modal movement receives its required damping rate. Damping rates are selected to optimize the frequency response of the system. This decoupled approach allows a separate analysis of the movements, and to adjust each vehicle movements appropriately. The graph below shows a typical frequency response of a conventional system, showing the usual under damped roll movement. The problem with the conventional system is the suspension geometry that makes roll damping very inefficient. Hard damping settings can fix the roll movement at the cost of impairing comfort, so there is no good tradeoff. The two conventional solutions can be seen in the grph below:
Vertical over damping problem has not only a negative impact on comfort, it overloads the tire with all suspension work as suspension will not absorb road irregularities (note how blue and red curves almost coincide, so all suspended mass movements equal the tire deflection). Soft settings leave roll movement totally uncontrolled. |
SYSTEM DESCRIPTION The ROLL CONTROL System is a hydropneumatic system installed on a vehicle axle, without sensors or actuators that reacts instantaneously to wheel movements. It is designed to provide separate response to each movement of the vehicle body such as roll and vertical movement appropriately for the vehicle distinct inertias. 
The ROLL CONTROL System consists of two hydraulic cylinders connected to damper unit by means of flexible hoses. Once the system is installed it is ready to work. The system removes the need for installing the anti-roll bar, when the damper fixtures can accommodate the antiroll forces. The extra roll stiffness increases the stability and keep an appropriate vertical movement dynamic response. It improves handling and reduces tire slip fluctuations. This ability to separate modal response beats all the conventional suspension compromises and tradeoffs that have been assumed at the design stage. Conventional suspensions cannot compensate the different body roll inertia with the same dampers that work. |
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ANTECEDENTS Motorhome, ambulance and minibuses manufacturers often use light trucks as chassis of their products, and they do the necessary changes to adapt them to the needs of the motorhome and ambulance market. These chassis normally incorporate conventional suspension systems based on the typical leaf springs and shock absorbers in the rear axle. Therefore, they get a suspension designed for the transportation of goods that did not take into consideration any comfort parameter that relate to the transportation of persons. These vehicles have a large roll inertia by design. This makes them prone to roll over, and become quite unstable at moderate driving speed. So far the only widely used solution is to adjust a conventional suspension to either stiffer damping, up to the point that it can reduce the roll movement and make driving safer, but totally uncomfortable, or soft enough for comfort and impairing stability. The ROLL CONTROL System can fix the problem and still soften the vertical movement and maintain the same level of comfort. Quite different damping values have to be set for either vertical or roll movements. The new frequency response we obtain for the softened vertical movements are: 
And for the roll movement, the increased damping rate controls the inertia and keeps resonant frequencies within an adequate range: 
Compression vs. Extension and low vs. high speed damping: The system can provide different damping to the upwards or downwards movement of the wheel as any conventional damper. This helps to optimize the system for human perception of comfort and handling some movements (i.e. roll and pitch) are more symmetric, while others (vertical) is normally chosen asymmetric. To cope with road bumps, the damping limits the max force like any conventional damping. Low speed settings are critical for the handling feelings for roll and pitch movements. So a different approach is normally implemented on each movement. |
SYSTEM IMPLEMENTATION The designed system is intended to replace the conventional suspension dampers and optionally the antiroll bar, setting the new vertical and roll suspension parameters This system solves the typical anomalies regarding roll adequate damping rate.
SUMMARY When comparing the ROLL CONTROL System with conventional systems we can easily find the following advantages: a)Body Control
b)Comfort & Safety:
c)Chassis design advantages:
These advantages are obtained with a basic working principle that is totally passive, simple and effective. The system does not incorporate sensors or actuators, thus providing an immediate reaction to the wheel movements. |
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AXLE CONTROL System (Top) 
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The AXLE CONTROL System, based on the CREUAT Suspension technology, is a single-axle hydropneumatic system that provides ride heigh control and extra roll stiffness. It does not include sensors or actuators, and reacts instantaneously to wheel movements improving the vehicle dynamics. It is designed to control the rear axle in two ways, first it separates the dynamic response to each movement of the vehicle body such as roll and vertical movement appropriately for the vehicle distinct inertias, and second it controls the ride height, so it lowers when entering patients., so the spring and damping rates can be optimized. |
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ANTECEDENTS Motorhomes, ambulances and minibuses are vehicles built for the transportation of injured and ill people, which often require driving fast on all kind of roads and streets, regardless of obstacles and weather conditions. Motorhome, ambulance and minibuses manufacturers often use light trucks as chassis of their products, and they do the necessary changes to adapt them to the needs of the motorhome, ambulance and minibuses market. These chassis normally incorporate conventional suspension systems based on the typical leaf springs and shock absorbers in the rear axle. Therefore, they get a suspension designed for the transportation of goods that did not take into consideration any comfort parameter that relate to the transportation of persons, let alone ill or injured ones. Motorhome, ambulance and minibuses design and weight distribution characteristics yield a vehicle with a rather high masses center, and rather large roll inertias. This makes them prone to roll over, and become quite unstable at moderate driving speed. Currently, the only way to adjust a conventional suspension is to make it stiffer, increasing the damping to the point that it can provide a controlled roll movement and make driving safer. The overall suspension stiffness is also shared by the vertical movement, thus compromising any comfort to the passengers up to the point it can become unbearable for critical ill people and the sanitary personnel attending them. SEPARATE SPRING AND DAMPING RATES As explained above the AXLE CONTROL System offers the possibility of setting different springs rates and different damping rates for each modal movement. A typical case would set soft vertical rates to increase roll damping adjusting it for the body inertia. The examples below shows the parameters chosen for a particular application: 
In this case, the location of the former dampers inside the chassis made it
necessary to use an extra high roll damping that would make it effective when translated to wheel rates.Softer vertical rates keep good comfort level. The different damping to roll and vertical movements are implemented in the hydraulic circuits include restrictors that act as selective dampers, so each modal movement receives its required damping rate. Damping rates are selected to optimize the frequency response of the system. This decoupled approach allows a separate analysis of the movements, and to adjust each vehicle movements appropriately. Frequency analysis: The main advantage of the system is its ability to provide different damping rates that compensate the different spring rates and inertias of each movement The ability to select different damping values permits the optimization of the frequency response for every modal movement. The graphs below show the frequency response curves for each movement: The graph below shows a typical frequency response of a conventional system, showing the usual under damped roll movement. The problem with the conventional system is the suspension geometry that makes roll damping very inefficient. Hard damping settings can fix the roll movement at the cost of impairing comfort, so there is no good tradeoff. The two conventional solutions can be seen in the grph below: 
Vertical over damping problem has not only a negative impact on comfort, it overloads the tire with all suspension work as suspension will not absorb road irregularities (note how blue and red curves almost coincide, so all suspended mass movements equal the tire deflection) Soft settings leave roll movement totally uncontrolled. The AXLE CONTROL System can fix the problem and still soften the vertical movement and maintain the same level of comfort. Quite different damping values have to be set for either vertical or roll movements. The new frequency response we obtain for the softened vertical movements are:
And for the roll movement, the increased damping rate controls the inertia and keeps resonant frequencies within an adequate range:
Compression vs. Extension and low vs. high speed damping: The system can provide different damping to the upwards or downwards movement of the wheel as any conventional damper. This helps to optimize the system for human perception of comfort and handling some movements (i.e. roll and pitch) are more symmetric, while others (vertical) is normally chosen asymmetric. To cope with road bumps, the damping limits the max force like any conventional damping. Low speed settings are critical for the handling feelings for roll and pitch movements. So a different approach is normally implemented on each movement. |
SYSTEM DESCRIPTION The AXLE CONTROL System, based on the Suspension technology patented by Creuat, is an interconnected suspension system, without sensors or actuators that reacts instantaneously to wheel movements. It is designed to separate the dynamic response to each movement of the vehicle body such as roll and vertical movement appropriately for the vehicle distinct inertias.
The AXLE CONTROL System consists of two simple-effect hydraulic cylinders connected to a central device by means of flexible hoses. Once the system is installed it is ready to work without further operations other than the vertical height regulation for load changes. The system removes the need for installing the anti-roll bar, which reduces weight and cost and can simplify the design of the chassis and its rigidity requirements.
The AXLE CONTROL System interconnects the two wheel movements through a central device. The system elastic elements are gas chambers, each associated to different each body movements, the stiffness to roll can be set different to the vertical movement. Same independency applies to the damping elements that are specific to separate body movement. This is why the system can increase the stability and keep an appropriate vertical movement dynamics. All in all it yields a better load distribution of weight among the wheels, improving handling due to the smaller tire slip fluctuations. This ability to separate modal response beats all the conventional suspension compromises and tradeoffs that have been assumed at the design stage. Conventional suspensions cannot compensate the different body roll inertia with the same dampers that work for the vertical movement. SYSTEM IMPLEMENTATION The designed system is intended to replace any other suspension and antiroll bar completely, taking care of the vertical and roll suspension parameters as well as the height regulation It is a passive and interconnected suspension system that controls independently the roll and vertical movement, and it allows the adjustment of each movement separately. In this way, we can optimize the system, making it stiff enough for roll to control the stability, and soft enough for the vertical movement to ensure the necessary comfort parameters. The system incorporates an hydraulic pump to compensate the load and control the ride height and make an easier access for injured/ill people and sanitary personnel. These system solves the typical anomalies in this kind of vehicle:
SUMMARY When comparing the AXLE CONTROL System with conventional systems we can easily find the following advantages: A)Body Control
B)Weight distribution
C)Comfort & Safety:
D)Chassis design advantages:
These advantages are obtained with a basic working principle that is totally passive, simple and effective. The system does not incorporate sensors or actuators, thus providing an immediate reaction to the wheel movements |
