Wheel slip control in heavy machinery such as loaders

Abstract

A piece of heavy machinery is provided, with a computer system and processing circuitry configured to obtain indications of a pitch angle of the machine, a speed of a wheel center relative ground surface, a rotational speed of the wheel and a loading of a bucket of the machine, to determine that there is a risk of over-slipping the wheel based on the indicated pitch angle and bucket loading, and in response to the determining perform longitudinal slip control for the wheel to avoid the over-slipping. A corresponding computer system, computer-implemented method, computer program product and computer-readable storage medium are also provided.

What is claimed is: 
     
         1 . A computer system for a piece of heavy machinery equipped with a bucket for scooping-up of material from a pile, wherein the computer system comprises processing circuitry configured to:
 obtain an indication of a pitch angle of the piece of heavy machinery relative to a surface on which the piece of heavy machinery is driven;   obtain an indication of a speed of a center of a wheel of the piece of heavy machinery parallel with the surface;   obtain an indication of a rotational speed of the wheel around its center;   obtain an indication of a loading force of the bucket;   based on the indicated pitch angle of the piece of heavy machinery and the loading force of the bucket, determine that there is a risk of over-slipping of the wheel; and   in response to determining the over-slipping risk, perform longitudinal slip control for the wheel to avoid the over-slipping of the wheel, wherein the slip control is performed based on a difference between a target longitudinal slip value and an actual longitudinal slip value for the wheel, wherein the target longitudinal slip value is obtained based on the indicated pitch angle of the piece of heavy machinery and loading force of the bucket, and wherein the actual longitudinal slip value is obtained based on the indicated rotational speed of the wheel around its center and the speed of center of the wheel parallel to the surface.   
     
     
         2 . The computer system of  claim 1 , wherein the processing circuitry is configured to determine that there is a risk of increased longitudinal slip based also on a requested torque for the wheel. 
     
     
         3 . The computer system of  claim 1 , wherein the processing circuitry is configured to obtain measurements of at least i) a distance between the piece of heavy machinery and a surface point and ii) a radial velocity of a surface point with respect to the piece of heavy machinery, and to obtain the indicated pitch angle based on the distance and to obtain the indicated speed of the center of the wheel parallel to the surface based on the indicated pitch angle and the radial velocity. 
     
     
         4 . The computer system of  claim 3 , wherein at least the radial velocity is obtained based on a signal from at least one radar sensor provided on the piece of heavy machinery. 
     
     
         5 . The computer system of  claim 1 , wherein to perform longitudinal slip control of the wheel includes limiting an allowed longitudinal slip of the wheel to a slip value below a slip threshold. 
     
     
         6 . The computer system of  claim 1 , wherein to determine that there is a risk of increased longitudinal slip, the processing circuitry is further configured to receive an indication about an ongoing or imminent entering of the bucket into the pile from an operator of the piece of heavy machinery. 
     
     
         7 . The computer system of  claim 1 , wherein to determine that there is a risk of increased longitudinal slip, the processing circuitry is further configured to receive an indication about at least one of: i) a transmission of the piece of heavy machinery being in a low gear, ii) an orientation of the bucket being parallel with the surface, and iii) the bucket being positioned at or close to the surface. 
     
     
         8 . The computer system of  claim 1 , wherein the processing circuitry is configured to obtain an estimated peak longitudinal slip value for the surface, and to determine the target longitudinal slip value as a slip value below or at the peak longitudinal slip value. 
     
     
         9 . The computer system of  claim 8 , wherein over-slipping of the wheel comprises the actual longitudinal slip value being above the peak longitudinal slip value. 
     
     
         10 . The computer system of  claim 1 , wherein the processing circuitry is further configured to, as part of determining the risk of over-slipping, use a machine learning model that has been trained to output a probability or indication of the risk for different combinations of at least pitch angle and loading of the bucket. 
     
     
         11 . A piece of heavy machinery, comprising:
 the computer system of  claim 1 , the wheel, and the bucket for scooping-up of material from a pile.   
     
     
         12 . The piece of heavy machinery of  claim 11 , wherein the piece of heavy machinery is a loader, such as a wheel loader. 
     
     
         13 . A computer-implemented method, comprising:
 obtaining, by processing circuitry of a computer system, an indication of a pitch angle of a piece of heavy machinery relative to a surface on which the piece of heavy machinery is driven;   obtaining, by the processing circuitry, an indication of a speed of a center of a wheel of the piece of heavy machinery parallel with the surface;   obtaining, by the processing circuitry, an indication of a rotational speed of the wheel around its center;   obtaining, by the processing circuitry, an indication of a loading force of a bucket of the piece of heavy machinery for scooping-up of material from a pile;   based on the indicated pitch angle of the piece of heavy machinery and loading force of the bucket, determining that there is a risk of over-slipping of the wheel; and   in response to the determining, performing longitudinal slip control for the wheel to avoid the over-slipping of the wheel, wherein the slip control is performed based on a difference between a target longitudinal slip value and an actual longitudinal slip value for the wheel, wherein the target longitudinal slip value is obtained based on the indicated pitch angle of the piece of heavy machinery and loading force of the bucket, and wherein the actual longitudinal slip value is obtained based on the indicated rotational speed of the wheel around its center and the speed of center of the wheel parallel to the surface.   
     
     
         14 . A non-transitory computer-readable storage medium comprising instructions which, when executed by the processing circuitry, cause the processing circuitry to perform the method of  claim 13 .