Patent Publication Number: US-2023150170-A1

Title: Probe and method for monitoring fresh concrete using an electromechanical actuator

Description:
FIELD 
     The improvements generally relate to handling fresh concrete received in a drum of a fresh concrete mixer, and more specifically relate to measuring information concerning the fresh concrete as the drum rotates. 
     BACKGROUND 
     Fresh concrete is formed of a mixture of ingredients including at least cement-based material and water in given proportions. The ingredients are typically transported inside a drum of mixer truck where the fresh concrete can be mixed prior to pouring thereof. 
     Even though mixer trucks can extend the life of fresh concrete, they do not make the fresh concrete last indefinitely. Typically, properties of the fresh concrete in the concrete mixer such as viscosity, yield, slump, air content and density can vary over time. The volume of fresh concrete received within the drum can also change, as it is also usual for mixer trucks to perform partial discharges on the go. As informed decision on how to handle the fresh concrete should be made based on measured information, there exists probes specifically designed for mixer trucks. Examples of such probes are described in U.S. Pat. No. 10,156,547 B2 and in published international patent application no. PCT/IB2010/054542, to name a few examples. 
     Although existing probes for mixer trucks or other fresh concrete mixers are satisfactory to a certain degree, there remains room for improvement. 
     SUMMARY 
     In an aspect, there is described a probe for monitoring fresh concrete received in a drum of a fresh concrete mixer such as a mixer truck, for instance. The probe generally has an electromechanical actuator with a frame mounted within the drum and a moving element actuatably mounted to the frame. The moving element has a fresh concrete interface which is exposed within the drum and which experiences a resistance to movement within the drum upon actuation of the electromechanical actuator with an electrical signal. The resistance experienced by the fresh concrete interface during the actuation can be stronger in presence of fresh concrete, weaker in presence of water and weakest in presence of air. A measurement unit is also provided. During use, the measurement circuit measures a resistance response during the actuation of the moving element and generates a response signal based on the measured resistance response. It is intended that the generated response signal has monitoring information concerning the fresh concrete and/or water within the drum, if any. In some embodiments, the measurement circuit includes an accelerometer measuring a mechanical response of the fresh concrete interface in which case the measured resistance response is mechanical. Additionally or alternately, the measurement circuit includes a power meter measuring the amount of electrical power consumed by the electromechanical during the actuation in which case the measured resistance response is electrical. 
     In accordance with a first aspect of the present disclosure, there is provided a probe for monitoring fresh concrete received in a drum of a fresh concrete mixer, the probe comprising: an electromechanical actuator having a frame mounted within the drum and a moving element actuatably mounted to the frame, the moving element having a fresh concrete interface exposed within said drum and experiencing a resistance to movement within said drum upon actuation of the electromechanical actuator with an electrical signal; and a measurement unit measuring a resistance response during said actuation and generating a response signal based on said measured resistance response, the generated response signal comprising monitoring information concerning the fresh concrete within the drum, if any. 
     Further in accordance with the first aspect of the present disclosure, the frame can for example be a housing enclosing the moving element, the housing can for example have at least a given wall with an inner side mechanically coupled to the moving element and an outer side acting as the fresh concrete interface. 
     Still further in accordance with the first aspect of the present disclosure, the given wall can for example be provided in the form of a membrane having a thickness below a given thickness threshold. 
     Still further in accordance with the first aspect of the present disclosure, the measurement unit can for example have an electrical response sensor measuring an electrical response of said electromechanical actuator during said actuation. 
     Still further in accordance with the first aspect of the present disclosure, the electrical response sensor can for example have an electrical power meter measuring an electrical power value indicative of an electrical power consumed by said electromechanical actuator during said actuation. 
     Still further in accordance with the first aspect of the present disclosure, the measurement unit can for example have a mechanical response sensor measuring a mechanical response of said electromechanical actuator during said actuation. 
     Still further in accordance with the first aspect of the present disclosure, the mechanical response sensor can for example have a position sensor measuring an amplitude value indicative of an amplitude of movement of said moving element during said actuation. 
     Still further in accordance with the first aspect of the present disclosure, the probe can for example further have a controller communicatively coupled to the measurement unit, the controller having a processor and a non-transitory memory having stored thereon instructions that when executed by the processor performs the step of monitoring the fresh concrete received in the drum based on said generated response signal. 
     Still further in accordance with the first aspect of the present disclosure, said actuation and measurement can for example be performed a plurality of times during at least a rotation of the drum, said monitoring can for example include determining a volume of the fresh concrete inside the drum based on said resistance responses experienced during the at least the rotation of the drum. 
     Still further in accordance with the first aspect of the present disclosure, said monitoring can for example include determining a rheological property of said fresh concrete, said rheological property can for example be selected in a group of rheological properties including viscosity, yield and slump. 
     Still further in accordance with the first aspect of the present disclosure, said monitoring can for example include determining a physical property of said fresh concrete, said physical property can for example be selected in a group of physical properties including air content and density. 
     Still further in accordance with the first aspect of the present disclosure, said monitoring can for example be based on calibration data pertaining to different resistance responses as function of different properties of the fresh concrete. 
     Still further in accordance with the first aspect of the present disclosure, said electrical signal is an oscillatory electrical signal having an amplitude oscillating over time, the resistance response experienced by the fresh concrete interface oscillating over time during said actuation with said oscillatory electrical signal. 
     Still further in accordance with the first aspect of the present disclosure, said oscillatory electrical signal can for example have a frequency ranging between about 20 Hz and about 20 kHz. 
     Still further in accordance with the first aspect of the present disclosure, the fresh concrete mixer can for example be a mixer truck. 
     In accordance with a second aspect of the present disclosure, there is provided a method of monitoring fresh concrete received in a drum of a fresh concrete mixer, the method comprising: exposing a fresh concrete interface within said drum; mechanically coupling a moving element of an electromechanical actuator to said fresh concrete interface; actuating the electromechanical actuator with an electrical signal, said actuating including moving said moving element relative to the fresh concrete interface, said moving element thereby experiencing a resistance to movement via said fresh concrete interface; measuring a resistance response during said actuating and generating a response signal based on said measured resistance response, the generated response signal comprising monitoring information concerning the fresh concrete within the drum, if any. 
     Further in accordance with the second aspect of the present disclosure, said measuring the resistance response can for example include measuring an electrical response of said electromechanical actuator during said actuation. 
     Still further in accordance with the second aspect of the present disclosure, said measuring the electrical response can for example include measuring an electrical power value indicative of an electrical power consumed by said electromechanical actuator during said actuation. 
     Still further in accordance with the second aspect of the present disclosure, said measuring the resistance response can for example include measuring a mechanical response of said electromechanical actuator during said actuation. 
     Still further in accordance with the second aspect of the present disclosure, said measuring the mechanical response can for example include measuring an amplitude value indicative of an amplitude of movement of said moving element during said actuation. 
     Still further in accordance with the second aspect of the present disclosure, the method can for example further comprise monitoring said fresh concrete based on the generated response signal. 
     Still further in accordance with the second aspect of the present disclosure, said actuating and said measuring can for example be performed a plurality of times during at least a rotation of the drum, said monitoring can for example include determining a volume of the fresh concrete inside the drum based on said resistance responses experienced during the at least the rotation of the drum. 
     Still further in accordance with the second aspect of the present disclosure, said monitoring can for example include determining a rheological property of said fresh concrete, said rheological property can for example be selected in a group of rheological properties including viscosity, yield and slump. 
     Still further in accordance with the second aspect of the present disclosure, said monitoring includes determining a physical property of said fresh concrete, said physical property can for example be selected in a group of physical properties including air content and density. 
     Still further in accordance with the second aspect of the present disclosure, said electrical signal can for example be an oscillatory electrical signal having an amplitude oscillating over time, said actuating can for example include moving said moving element against the fresh concrete interface in at least a back and forth sequence. 
     Still further in accordance with the second aspect of the present disclosure, the fresh concrete mixer can for example be a mixer truck. 
     Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       In the figures, 
         FIG.  1    is a schematic view of an example of a system for monitoring fresh concrete received in a drum of a mixer truck, with a probe mounted inside the drum and a controller, in accordance with one or more embodiments; 
         FIG.  2    is a sectional view of the drum of  FIG.  1   , taken along section  2 - 2  of  FIG.  1   , in accordance with one or more embodiments; 
         FIG.  3    is a block diagram of the system of  FIG.  1   , with the probe having an electromechanical actuator and a measurement unit measuring a mechanical response of the electromechanical actuator, in accordance with one or more embodiments; 
         FIG.  4    is a schematic view of an example of a computing device of the controller of  FIG.  1   , in accordance with one or more embodiments; 
         FIG.  5 A  is a sectional view of an example of a probe for monitoring fresh concrete received in a drum of a mixer truck, showing a housing having a given wall acting as a fresh concrete interface, in accordance with one or more embodiments; 
         FIG.  5 B  is a top view of the probe of  FIG.  5 A , in accordance with one or more embodiments; 
         FIG.  6    is a schematic view of a system incorporating the probe of  FIG.  5 A  and a controller, in accordance with one or more embodiments; 
         FIG.  7 A  is a graph showing average accelerometer magnitude as function of a frequency of the oscillatory signal, in accordance with one or more embodiments; 
         FIG.  7 B  is a graph showing integral values of the average accelerometer magnitudes of  FIG.  7 A  as integrated over a given frequency band, in accordance with one or more embodiments; 
         FIG.  8 A  is a graph showing average accelerometer magnitude as function of a frequency of the oscillatory signal, in accordance with one or more embodiments; 
         FIG.  8 B  is a graph showing integral values of the average accelerometer magnitudes of  FIG.  8 A  as integrated over a given frequency band, in accordance with one or more embodiments; and 
         FIG.  9    is a block diagram of an example of a system for monitoring fresh concrete received in a drum of a mixer truck, with a probe having an electromechanical actuator and a measurement unit measuring an electrical response of the electromechanical actuator, in accordance with one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows an example of a fresh concrete mixer truck  10  (hereinafter referred to as “the mixer truck  10 ”) for handling fresh concrete  12 . As shown, the mixer truck  10  has a truck frame  14  and a rotating drum  16  which is rotatably mounted to the truck frame  14 . As such, the drum  16  can be rotated about a rotation axis  18  which is at least partially horizontally-oriented relative to the vertical  20 . 
     As illustrated, the drum  16  has inwardly protruding blades  22  mounted inside the drum  16  which, when the drum  16  is rotated in an unloading direction, force the fresh concrete  12  along a discharge direction  24  towards a discharge outlet  26  of the drum  16  so as to be discharged at a job site, for instance. In contrast, when the drum  16  is rotated in a mixing direction, opposite to the unloading direction, the fresh concrete  12  is kept and mixed inside the drum  16 . 
     In some embodiments, concrete constituents (e.g., cement, aggregate and water) are loaded in the drum  16  after which the drum  16  can be rotated a certain number of rotations in the mixing direction at a certain rotation speed so as to suitably mix the concrete constituents to one another, thus yielding the fresh concrete  12 . In other embodiments, already mixed fresh concrete is loaded inside the drum  16 , in which case the fresh concrete  12  can still be further mixed inside the drum  16  before discharge. 
     As shown, the mixer truck has a system  100  for monitoring the fresh concrete  12  received in the drum  16  of the mixer truck  10 . As will be described below, the system  100  can be used to measure information pertaining to the fresh concrete  12  received in the drum  16 . The measured information can then be used to handle the fresh concrete  12  satisfactorily. Examples of the information measured by the system  100  can include, but not limited to, physical properties (e.g., air content, density, temperature), rheological properties (e.g., viscosity, yield, slump), or other information concerning the fresh concrete  12  such as the volume of fresh concrete  12  received in the drum  16  at a given moment in time. Based on the monitored information, the fresh concrete  12  can be handled by, for instance, adding water into the drum  16 , adding concrete constituents into the drum  16 , adding adjuvant(s) in the drum  16 , mixing the concrete constituents at a high speed range for a given of drum rotations, agitating the fresh concrete at a low speed range for a given period of time, and wholly or partially discharging the fresh concrete  12  at a job site. 
     As depicted in this embodiment, the system  100  has a probe  102  having an electromechanical actuator  104  actuatable within the fresh concrete  12  and a measurement unit  106  measuring a response of the electromechanical actuator  104  during actuation. The system  100  also incorporates a controller  108  communicatively coupled to the probe  102  for monitoring the fresh concrete  12  based on the measured response. 
     As illustrated, the controller  108  is mounted to the truck frame  14 . In this specific example, the controller  104  is mounted inside a cabin of the mixer truck  10 , and has a user interface  110  receiving and/or displaying information or alarms in this example. Although the controller  108  is on-truck, and even in-cabin in the illustrated embodiment, it is noted that the controller  108  can be remote from the mixer truck  10  in which case the communication between the controller  108  and the probe  102  can be wireless. In some embodiments, the controller  108  can be omitted. 
     As best seen in  FIG.  2   , the electromechanical actuator  104  has a probe frame  112  which is fixedly mounted to the drum  16 . Accordingly, as the drum  16  is rotated, the electromechanical actuator  104  rotates with it in a circumferential manner across successive circumferential positions. For reference, the probe shown in  FIG.  2    is located at an arbitrary circumferential position of 180°, i.e., at the bottom of the drum  16 . In this example, the drum  16  may have an opening  114  partially or wholly receiving the probe frame  112 . However, the probe frame  112  is itself fixedly mounted to an inner wall  30  of the drum in some other embodiments. 
     The electromechanical actuator  104  has a moving element  116  which is actuatably mounted to the probe frame  112 . Accordingly, upon actuation of the electromechanical actuator  104  with an electrical signal, the electromechanical actuator  104  can convert the electrical energy carried by the electrical signal into mechanical energy through movement of the moving element  116 . Examples of such electromechanical actuator  104  can include, but not limited to, a linear movement actuator, a rotational movement motor, a vibratory actuator, a voice coil, a piezoelectric element, a camshaft, a crankshaft and the like. 
     As shown in this example, the moving element  116  has a fresh concrete interface  118  exposed within the drum  16 . It is intended that the fresh concrete interface  118  can be exposed the fresh concrete  12  within the drum  16 . Indeed, as the drum  16  rotates over time, the electromechanical actuator  104  can move to some circumferential positions where the fresh concrete interface  118  is immersed in the fresh concrete  12 , e.g., when the probe  102  is at the bottom of the drum  16 . However, at some other circumferential positions, the fresh concrete interface  118  may be exposed to air, e.g., when the probe  102  is at the top of the drum  16 , Accordingly, the fresh concrete interface  118  will always be exposed to a surrounding substance which will at some circumferential positions of the drum  16  be the fresh concrete  12 , or air  32  elsewhere. In both cases, upon actuation of the electromechanical actuator  104  with an electrical signal, the fresh concrete interface  118  of the moving element  116  experiences a resistance to movement as it is moved through the surrounding substance within the drum  16 . 
     The measurement unit  106  measures a response of the electromechanical actuator  104  to this resistance (hereinafter “the resistance response”) during the actuation, and generates a response signal based on the measured resistance response. As the resistance response is indicative of the resistance to movement of the fresh concrete interface  118  relative to the surrounding substance, the generated response signal carries information concerning the fresh concrete  12  within the drum  16 , if any. Whether the resistance response is greater or weaker upon actuation with a given electrical signal can help monitoring the fresh concrete  12  within the drum  16 , as will be described in the following paragraphs. 
     Example information that can be measured and monitored using the probe  102  are described below:
         In some embodiments, the measured resistance response can be used to determine whether the probe  102  is exposed to fresh concrete  12  or to air  32  within the drum  16 . For instance, the controller can determine that the probe  102  is exposed to fresh concrete  12  when the measured resistance response is above (or below) a given threshold t 1 . In contrast, the controller can determine that the probe  102  is exposed to air  32  when the measured resistance response is below (or above) a given threshold t 1 . In some embodiments, the given threshold t 1  can be 0.2 (normalized arbitrary units), in which case it may be determined that the probe  102  is exposed to fresh concrete  12  when the measured resistance response is 0.5 (or 0.1) or to air  32  when the measured resistance response is 0.1 (or 0.5). Depending on the embodiment, alarm(s) may be generated by the controller upon determining that the probe  102  is exposed to air, for instance.   In some embodiments, the measured resistance response can be used to determine whether the probe  102  is exposed to fresh concrete  12 , water or air within the drum  16 , For instance, the controller can determine that the probe  102  is exposed to fresh concrete  12  when the measured resistance response is above (or below) both first and second thresholds t 1  and t 2 . In contrast, the controller can determine that the probe  102  is exposed to air when the measured resistance response is below (or above) the first and second thresholds t 1  and t 2 . When the measured resistance response is between the first and second thresholds t 1  and t 2 , the controller can determine that the probe  102  is exposed to water, as the density of water is higher than a density of air but lower than a density of fresh concrete. Depending on the embodiment, alarm(s) may be generated by the controller upon determining that the probe  102  is exposed to air or water, for instance.   In some embodiments, the measured resistance response can be monitored as the drum  16  rotates. Therefore, a given number of measured resistance responses can be measured at a corresponding number of timestamps or circumferential positions of the drum  16 . The probe  102  may incorporate a probe location sensor such as one or more accelerometers measuring directly or indirectly a circumferential position of the probe  102  at any given time for association to corresponding measured resistance responses. In these embodiments, the circumferential positions at which the probe  102  enters and exits the fresh concrete  12  can be determined by monitoring at which circumferential position the resistance responses, as measured during a single rotation of the drum  16 , crosses and crosses back the given threshold t 1 . However, in some other embodiments, the probe location sensor may be omitted. Regardless of whether a probe location sensor is used, the measured resistance responses can be used to determine at which circumferential positions θ enter  and θ exit  of the drum  16  the probe  102  enters and exits the fresh concrete  12 . For instance, the controller can determine that, during a given rotation of the drum  16 , the measured resistance responses indicate that the probe  102  has remained immersed within the fresh concrete  12  for a given duration Δt. In some embodiments, the duration Δt indicates, for resistance responses measured within a single rotation of the drum  16 , a timestamp difference between a timestamp where the measured response crosses the given threshold t 1  and another timestamp where the measured responses crosses back the given threshold t 1 . A curve may be fitted to the measured resistance responses and then solved to obtain its intersection with the given threshold t 1  in some other embodiments. The duration Δt may advantageously be normalized based on a rotational speed of the drum  16 , if deemed necessary. In some embodiments, such information can then be compared to calibration data to retrieve the circumferential positions θ enter  and θ exit  at which the probe  102  enters or exists the fresh concrete  12 . Table 1 presented below shows exemplary calibration data for such measurements.       

     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Exemplary calibration data for determining at which Θ enter   
               
               
                 and Θ exit  of the drum 16 the probe 102 enters or exits the fresh concrete 12 
               
            
           
           
               
               
            
               
                   
                 Circumferential positions 
               
               
                 Measured duration Δt 
                 Θ enter  and Θ exit   
               
               
                 [seconds] 
                 [degrees] 
               
               
                   
               
            
           
           
               
               
            
               
                 0 
                 none 
               
               
                 10 
                 90 and 270 
               
               
                 15 
                 45 and 315 
               
               
                   
               
               
                 Assuming a rotational speed of the drum of about 3 RPM. 
               
            
           
         
       
     
     In some embodiments, the circumferential positions θ enter  and θ exit  at which the probe  102  enters and exits the fresh concrete  12  can be compared to calibration data to retrieve a volume value indicative of a volume of the fresh concrete  12  within the drum  16 . Table 2 presented below shows exemplary calibration data for such measurements. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Exemplary calibration data for determining the 
               
               
                 volume of fresh concrete inside the drum 
               
            
           
           
               
               
               
            
               
                   
                 Circumferential positions 
                   
               
               
                   
                 Θ enter  and Θ exit   
                 Volume value 
               
               
                   
                 [degrees] 
                 [m 3 ] 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 none 
                 0 
               
               
                   
                 135 and 225 
                 1 
               
               
                   
                  90 and 270 
                 3 
               
               
                   
                   
               
               
                   
                 For a drum having a capacity of about 6 m 3   
               
            
           
         
       
         
         
           
             In some embodiments, the measured resistance response can be used to determine a property of the fresh concrete  12  to which the fresh concrete interface  118  is exposed. For instance, experiments have confirmed that, assuming that the rotational speed of the drum  16 , the amount of concrete above the probe  102 , the viscosity, the yield and the temperature of the fresh concrete  12  are constant for the fresh concrete  12  received the drum  16 , one can compare the measured resistance response to calibration data in order to determine an air content value indicative of an air content of the fresh concrete  12  within the drum  16 . Table 3 presented below shows exemplary calibration data for such measurements. 
           
         
       
    
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Exemplary calibration data for determining the 
               
               
                 air content of fresh concrete inside the drum 
               
            
           
           
               
               
               
            
               
                   
                 Measured resistance 
                   
               
               
                   
                 response 
                 Air content value 
               
               
                   
                 [normalized arbitrary unit] 
                 [%] 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0.20 
                 0 
               
               
                   
                 0.22 
                 2 
               
               
                   
                 0.24 
                 4 
               
               
                   
                   
               
               
                   
                 Assuming constant viscosity, yield and temperature 
               
            
           
         
       
     
     In at least some situations, the fresh concrete  12  can be air-entrained meaning that the fresh concrete  12  contains a significant numbers (e.g., billions) of microscopic air voids per cubic foot. It is known that these air voids can relieve internal pressure inside the fresh concrete  12  by providing tiny chambers within the fresh concrete  12 . It was found that these tiny chambers, e.g., their volumes and/or density, may influence the resistance of the fresh concrete  12  to the movement of the fresh concrete interface  118  of the probe  102 . It is noted that these tiny chambers can receive water and then expand in freezing temperatures. As a consequence, monitoring air content within a given batch of fresh concrete has been found to be particularly relevant in the context of northern climates where freezing and thawing cycles effects are not insignificant. 
     In some embodiments, it is predicted that the measured resistance response could also be used to determine other types of property of the fresh concrete  12  to which the fresh concrete interface  118  is exposed. For instance, it is predicted that, assuming that the rotational speed of the drum  16 , the amount of concrete above the probe  102 , the air content, the yield and the temperature of the fresh concrete  12  are constant for the fresh concrete  12  received the drum  16 , one can compare the measured resistance response to calibration data in order to determine a viscosity value indicative of a viscosity of the fresh concrete  12  within the drum  16 . Table 4 presented below shows exemplary calibration data for such measurements. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Exemplary calibration data for determining the 
               
               
                 viscosity of fresh concrete inside the drum 
               
            
           
           
               
               
               
            
               
                   
                 Measured resistance 
                   
               
               
                   
                 response 
                 Viscosity value 
               
               
                   
                 [normalized arbitrary unit] 
                 [arbitrary unit] 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0.20 
                 1 
               
               
                   
                 0.22 
                 2 
               
               
                   
                 0.24 
                 3 
               
               
                   
                   
               
               
                   
                 Assuming constant air content, yield and temperature 
               
            
           
         
       
     
     In some other embodiments, it is predicted that, assuming that the rotational speed of the drum  16 , the amount of concrete above, the air content, the viscosity and the temperature of the fresh concrete  12  are constant for the fresh concrete  12  received the drum  16 , one can compare the measured resistance response to calibration data in order to determine a yield value indicative of a yield of the fresh concrete  12  within the drum  16 . Table 5 presented below shows exemplary calibration data for such measurements. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Exemplary calibration data for determining 
               
               
                 the yield of fresh concrete inside the drum 
               
            
           
           
               
               
               
            
               
                   
                 Measured response 
                 Yield value 
               
               
                   
                 [normalized arbitrary unit] 
                 [kPa] 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0.20 
                 10 
               
               
                   
                 0.22 
                 12.5 
               
               
                   
                 0.24 
                 15 
               
               
                   
                   
               
               
                   
                 Assuming constant air content viscosity and temperature 
               
            
           
         
       
     
     Depending on the embodiment of the measurement unit  106 , it is noted that the resistance response can be measured as either one or both of a mechanical response and an electrical response. 
     In the case where the resistance response is mechanical, the measurement unit  106  can have a position sensor measuring a mechanical response of the electromechanical actuator  104  during the actuation. In such a case, the mechanical response typically has an amplitude value indicative of an amplitude of movement of the moving element during the actuation. For a given electrical signal, the amplitude of movement of the moving element  116  may be greater when the surrounding substance is air  32  than when it is fresh concrete  12 , as fresh concrete  12  will likely offer more resistance to movement than air  32 . Accordingly, the measured response can indicate whether the probe  102  is immersed into the fresh concrete  12  or air  32 , for instance. 
     In the case where the resistance response is electrical, the measurement unit  106  can have an electrical power meter which measures an electrical response of the electromechanical actuator  104  during the actuation. As such, the electrical response can comprise an electrical power value indicative of an electrical power consumed by the electromechanical actuator  104  during the actuation. In at least some circumstances, the electrical power consumed by the electromechanical actuator  104  may be greater when the surrounding substance is fresh concrete than air, as fresh concrete will offer much more resistance to movement than air. It is noted that such proportionality may not be always applicable, as sometimes an oscillatory electrical signal may create a natural resonance response of the fresh concrete interface  118  relative to the surrounding substance, in which case the electromechanical actuator  104  may consume less electrical power than when out-resonance. 
     It will be appreciated that the given threshold t 1  and the calibration data presented above have been presented as examples only. It is clear that depending on whether the measured resistance response is mechanical or electrical, the calibration data can differ. For instance, a measured resistance response being greater than the given threshold t 1  can indicate that the probe  102  is exposed to air when the measured resistance response is mechanical, as the fresh concrete interface  118  may move farther away from its rest position for a given electrical signal. However, a measured resistance response being greater than the given threshold t 1  can indicate that the probe  102  is exposed to fresh concrete  12  when the measured resistance response is electrical, as moving the fresh concrete interface  118  against the fresh concrete  12  may require more electrical power. 
     As will be described in the next paragraphs, the probe  102  measures a resistance response that is mechanical. Another probe embodiment measuring an electrical resistance response will be described below with reference to  FIG.  9   . 
       FIG.  3    shows a block diagram of the probe, in accordance with one or more embodiments. As depicted, the moving element  116  of the electromechanical actuator  104  is coupled to the fresh concrete interface  118  via a mechanical coupling  132 . An example of mechanical coupling can include, but not limited, to a direct or indirect physical coupling, a spring-loaded coupling, a damped-coupling, and the like. 
     As shown, the probe frame  112  is provided in the form of a housing  120  inwardly protruding from the inner wall  30  the drum  16 . As shown, the housing  130  encloses at least the moving element  116  and the measurement unit  106 . In this example, the housing  120  has at least a given wall  122  with an inner side  118   a  being mechanically coupled to the movement element  116 , and an outer side  118   b  acting as the fresh concrete interface  118 . In this way, upon actuation of the electromechanical actuator  104 , the moving element  116  moves against the given wall  122  which in turn causes the fresh concrete interface  118  to move against the surrounding substrate inside the drum  16 . In such embodiments, the fresh concrete interface  118  is part of the moving element  116  as they are mechanically coupled (e.g., made integral) to one another. In some embodiments, the given wall  122  is provided in the form of a vibratory membrane  124  having a thickness t below a given thickness threshold. For instance, in some embodiments, the vibratory membrane  124  is made of steel and has a thickness t of about 1 mm. In this example, the vibratory membrane  124  is sealingly mounted to the given wall  122  via an urethane seal to allow vibratory movement. In such embodiments, the electromechanical actuator  104  can be analogous to an electroacoustic transducer and the like. 
     The electrical signal with which the electromechanical actuator  104  is actuated can vary from one embodiment to another. For instance, the electrical signal can have a fixed amplitude, a time-varying amplitude and/or an oscillatory-varying amplitude. When the electrical signal is an oscillatory electrical signal having an amplitude oscillating over time, the resistance response experienced by the fresh concrete interface  118  can oscillate over time correspondingly. The frequency at which the oscillatory-varying amplitude of the electrical signal can vary from an embodiment to another. For instance, the oscillatory electrical signal can have a frequency ranging between about 0 Hz and about 50 kHz, preferably between about 20 Hz and about 20 kHz, and most preferably between about 100 Hz and about 2000 Hz. The frequency can be swept across a given frequency range in some embodiments. In embodiments where the electromechanical actuator  104  is provided in the form of an electroacoustic transducer, the frequency of the electrical signal can vary from 20 Hz to 20 kHz. 
     In this embodiment, the measurement unit  106  includes one or more mechanical response sensors such as position sensor  134  which is in this case mechanically coupled to the fresh concrete interface  118 . Examples of such mechanical response sensors include, but not limited to, magnitude sensor(s), speed sensor(s), accelerometer(s) and the like. These mechanical response sensors can be based on one or more different technologies such as piezoelectric, microelectromechanical systems-(MEMS), optical, capacitive, and inductive, or any combination thereof. The position sensor  134  shown in this example is provided in the form of one or more accelerometers measuring acceleration in one or more orthogonal axes as the fresh concrete interface  118  is being moved against the surrounding substance, and generating a corresponding response signal. 
     In this specific embodiment, the system  100  has a communication unit  136  receiving the response signal generated by the position sensor  134  and transmitting it towards a communication unit  140  of the controller  108 , which is on-truck in this embodiment. Upon receiving the generated response signal, the controller can then send instructions and/or store the generated response signal, for monitoring the fresh concrete  12  right away or later. 
     As depicted, a signal generator  142  is provided to generate the electrical signal with which the electromechanical actuator  104  is to be actuated. The signal generator  142  is remote from the housing  120  in this embodiment. However, in some other embodiments, the signal generator  142  can be enclosed within the housing  120 . The signal generator  142  can be configured to generate electrical signals of different amplitudes, frequencies, durations, and/or of any arbitrary shape. For instance, the electrical signal(s) can have any suitable type of shape including, but not limited to, an impulse shape, a step shape, a harmonic shape and the like. In some embodiments, the controller  108  is communicatively coupled with the signal generator  142  and sends instructions to the signal generator  142  concerning the electrical signal to be generated. 
     The system  100  can have a power source  144  powering the components. In this example, the power source  144  is remote from the housing  120 . However, in some other embodiments, the power source  144  can be enclosed in the housing  120 . In such embodiments, the power source  144  can be provided in the form of a battery or battery pack and/or solar panel. It is intended that the power source  144  powers the signal generator  142 , the electromechanical actuator  104 , the measurement system  106  and/or other components of the system  100 . In some other embodiments, the power source  144  is provided in the form of a power supply drawing power from a battery of the mixer truck. 
     The controller  108  can be provided as a combination of hardware and software components. The hardware components can be implemented in the form of a computing device  400 , an example of which is described with reference to  FIG.  4   . 
     Referring to  FIG.  4   , the computing device  400  can have a processor  402 , a memory  404 , and I/O interface  406 . Instructions  408  for monitoring the fresh concrete  12  can be stored on the memory  404  and accessible by the processor  402 . 
     The processor  402  can be, for example, a general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), or any combination thereof. 
     The memory  404  can include a suitable combination of any type of computer-readable, non-transitory memory that is located either internally or externally such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CAROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. 
     Each I/O interface  406  enables the computing device  400  to interconnect with one or more input devices, such as mouse(s), keyboard(s), position sensor(s), power meter(s), or with one or more output devices such as a user interface, a non-transitory memory or a remote network. In some embodiments, the user interface is configured to generate alarm(s) based on the generated response signal. It is intended that these alarm(s) may be generated based on a comparison of the generated response signal to reference data, for instance, Such alarm(s) can be visual, auditory, vibratory and the like. 
     Each I/O interface  406  enables the controller  108  to communicate with other components, to exchange data with other components, to access and connect to network resources, to serve applications, and perform other computing applications by connecting to a network (or multiple networks) capable of carrying data including the Internet, Ethernet, plain old telephone service (POTS) line, public switch telephone network (PSTN), integrated services digital network (ISDN), digital subscriber line (DSL), coaxial cable, fiber optics, satellite, mobile, wireless (e.g. Wi-Fi, WiMAX), SS7 signaling network, fixed line, local area network, wide area network, and others, including any combination of these. 
     The computing device  400  described above are meant to be examples only. Other suitable embodiments of the controller  108  can also be provided, as it will be apparent to the skilled reader. 
       FIGS.  5 A and  6 B  show another example of a probe  502  for monitoring fresh concrete received in a drum  16  of a mixer truck, in accordance with one or more embodiments. As shown, the probe  502  has an electromechanical actuator  504  with a frame  512  mounted to the inner wall  30  within the drum  16  and a moving element actuatably mounted to the frame  512 . In this example, the frame  512  is a housing  520  enclosing at least the moving element. 
     As best shown in  FIG.  5 A , the housing  520  has a given wall  522  with an inner side mechanically coupled to the moving element and an outer side acting as a fresh concrete interface  118  of the electromechanical actuator  504 . The wall is provided in the form of a membrane  524  with a thickness below a given thickness threshold. As such, the fresh concrete interface  118  exposed within the drum will, during use, experience a resistance to movement within the drum  16  upon actuation of the electromechanical actuator  104  with an electrical signal. 
     As illustrated, the probe  502  has a measurement unit  506  comprising a position sensor  534  measuring a mechanical response of the electromechanical actuator  504 . More specifically, in this embodiment, the mechanical response that is measured includes an amplitude value indicative of an amplitude of movement of the moving element during the actuation. 
     Referring now to  FIG.  6   , a block diagram of a system  600  incorporating the probe  502  is shown. As depicted in this example, the system  600  includes a controller  608  which is communicatively coupled to the electromechanical actuator  504  and to the measurement unit  506 . The controller  608  is provided in the form of a data acquisition system of the type National Instrument cDAQ 9178 in this example. The data acquisition system can be powered using a 110V supply line and has a Universal Serial Bus (USB) port. The data acquisition system in this example has a signal generator  544  of the type National Instrument 9263. An electrical amplifier  546  is used to amplify the electrical signal initially generated by the data acquisition system via electrical cable(s). The electromechanical actuator  504  receives the amplified electrical signal via electrical cable(s). Such components can be integrated on a custom printed circuit board (PCB) that can include any other type of desirable electronic components such as wireless communication units and the like. 
     As shown, the position sensor  534  generates a response signal which is communicated back to the data acquisition system. More specifically, the data acquisition system has an acousto-vibratory detector  548  of the type National Instrument 9234 which is connected to the position sensor  534  via cable(s). 
       FIGS.  7 A through  8 B  show data measured using the system  600 , in one or more experiments. 
     More specifically,  FIG.  7 A  is a graph showing amplitudes values as measured by the position sensor  534  in the axis of movement of the moving element as function of a frequency of the electrical signal with which the electromechanical actuator  504  is actuated for fresh concrete samples of different air content values. As shown, for each fresh concrete sample, the probe  502  was used to measure a mechanical resistance response of the electromechanical actuator  504  during actuation with an electrical signal having a frequency swept from 250 Hz to 859 Hz. As shown, one can notice that in the frequency band ranging from 350 Hz to 650 Hz, the behaviour of the measured resistance response is relatively proportional to the air content value of the corresponding fresh concrete sample. This relationship is better shown in  FIG.  7 B  which shows integrated values of the curves of  FIG.  7 A  over this frequency band. One can appreciate a relatively linear relationship, which can be used as a basis for calibration data such as those described above. 
     It is noted that, in this experiment, the fresh concrete samples have properties assumed to be constant except for air content. More specifically, a first fresh concrete sample of given properties (including an air content value of 2.4%) was tested using the probe, then air-entraining adjuvants was added to the first fresh concrete sample to increase the air content to a second air content value of 6.1%, and so forth, for two other iterations. Accordingly, the four fresh concrete samples had similar properties except for their air content. Accordingly, the measured resistance response can be associated to the air content, at least in situations where the other properties of the fresh concrete match with the properties of the fresh concrete used to determine the calibration data. 
     Although the example above relates to air content, it is predicted that similar conclusions may be reached for other properties such as viscosity, yield and the like. 
       FIG.  8 A  shows a graph similar to the one shown in  FIG.  7 A , but for different fresh concrete samples. Again, a proportional relationship is obtained between the magnitude value and the air content, as emphasized in  FIG.  8 B . 
       FIG.  9    shows another example of a probe  902  for monitoring fresh concrete received in a drum  16  of a mixer truck. As shown, the probe  902  has an electromechanical actuator  904  with a frame  912  mounted to the drum  16  and a moving element  916  actuatably mounted to the frame  912 . Similarly to the embodiments described above, the moving element  916  has a fresh concrete interface  918  exposed within the drum  16  and experiencing a resistance to movement within the drum  16  upon actuation of the electromechanical actuator  904  with an electrical signal. A measurement unit  906  is provided to measure the resistance response during the actuation, and to generate a corresponding response signal. 
     In this specific embodiment, instead of measuring a mechanical response, the measurement unit  906  rather measures an electrical response of the actuation. More specifically, the measurement unit  906  has an electrical response sensor, in this case provided in the form of an electrical power meter  950 , measuring an electrical response of the electromechanical actuator  904  during the actuation. In this example, the electrical response has an electrical power value indicative of an electrical power consumed by the electromechanical actuator  904  during the actuation. The power meter  950  can be provided in different shape or form. Specifically, in this embodiment, the power meter  950  measures the voltage supplied to the electromechanical actuator using a voltmeter  952  for instance. Moreover, the power meter  950  measures a current that is flowed through the electromechanical actuator  904  using an ammeter  954 , for instance. In view of the relation P=VI, wherein P denotes the electrical power value, V denotes the voltage value and I denotes the current value, the controller  908  can monitor the amount of electricity consumed during actuation of the electromechanical actuator  904 . 
     As shown in this embodiment, the frame  912  is provided in the form of a housing  920  enclosing a power source  944 , a signal generator  942 , the electromechanical actuator  904 , the measurement unit  906  and the controller  908 . 
     As can be understood, a given measurement unit may incorporate both the position sensor and the power meter to monitor both the mechanical and the electrical resistance response of the electromechanical actuator. In these embodiments, a property such as air content may be determined using the mechanical resistance response, and proof-reviewed upon determination of the same property but using the electrical resistance response instead, or vice-versa. 
     As can be understood, the examples described above and illustrated are intended to be exemplary only. For instance, although the system(s) described herein are installed to a mixer truck in this example, the system disclosed herein can be installed on any type of fresh concrete mixers including, but not limited to, stationary mixers, batch mixers, drum type mixers, tilting drum mixers, non-tilting drum mixers, reversing drum mixers, pan type mixers, continuous mixer trucks and the like. The type of measurement unit is not limited to the position sensor and/or to the power meter described above as other types of measurements units can be used as well to monitor a mechanical response and/or an electrical response of the electromechanical actuator in some other embodiments. The scope is indicated by the appended claims.