Control method and control system for agitating mechanism

This non-provisional patent application claims priority under 35 U.S.C. § 119(a) from Patent Application No. 201510472780.4 filed in The People's Republic of China on Aug. 4, 2015.

The present invention relates to method and system for controlling a rotation process of an agitating mechanism such as a food mixer, and in particular to the control of a motor-driven food mixer.

A known agitating mechanism, such as the agitating mechanism of a food mixer, rotates in a fixed single direction, or can be direction-reversed. However, the direction reverse is achieved either by manual trigger or according to a fixed time period.

In real life, when some agitating mechanisms are used to agitate blocky solid food such as vegetables and meat blocks, or food containing the solid blocks, agitating blades of the agitating mechanism may be resisted by the blocks. The agitating mechanism usually operates with a preset or user-selected power which is constant. When the agitating blades are resisted by the solid blocks, the rotation speed becomes very slow or even the agitating mechanism becomes stalled which is referred to as being jammed. If the jam lasts a little long, it may cause the agitating mechanism (e.g. the motor) or other electrical components to be burnt out. Even if the agitating blades of the agitating mechanism forcefully breaks through the resistance of the solid blocks, this over-forceful driving manner can seriously damage the texture of the food being agitated, which reduces visual enjoyability of the food, affects user's appetite, degrades the user experience, and shortens the life of the agitating mechanism.

Some other agitating mechanisms are used to agitate mushy and viscous food such as milkshake or salad, and usually ice blocks are added to the food to be agitated at the same time. During agitation, high rotation speed agitating blades (cutter blades) form a blocking layer, which makes the viscous food unable to be sufficiently agitated and always remain above the blocking layer of the cutter blades. As such, a cavity is formed in the agitated substance at the area of the blocking layer, which looks like an air bubble in the agitated substance. The cavity does not hinder the agitation of the agitating mechanism. However, the cavity makes the substance unable to be homogenously agitated, such that fine agitation cannot be achieved, which can easily result in lumps being formed in the agitated substance.

Thus, there is a desire for a control method and a control system for an agitating mechanism which can address at least one of the forgoing problems.

In one aspect, a control method for an agitating mechanism is provided. The control method includes:

an electrical current obtaining step s 1 of receiving a load current detected by a current detecting apparatus when the agitating mechanism is rotating along a specific direction;

a trigger determination step s 2 of determining whether the rotation of the agitating mechanism meets a preset trigger condition based on the load current; and

a rotation control step s 3 of controlling the agitating mechanism to rotate in a direction opposite from the specific direction when the trigger condition is met.

In another aspect, a control system for the agitating mechanism is provided, which includes:

an electrical current obtaining module configured to receive a load current detected by a current detecting apparatus when the agitating mechanism is rotating along a specific direction;

a trigger determination module configured to determine whether the rotation of the agitating mechanism meets a preset trigger condition based on the load current; and

a rotation control module configured to control the agitating mechanism to rotate in a direction opposite from the specific direction when the trigger condition is met.

The present invention has the following advantages: the present invention can automatically reverse the direction according to actual situations during the agitating operation and can therefore handle special situations by itself; the present invention can reduce the possibility of the electrical components of the agitating mechanism being burnt out and prolongs the lifespan of the agitating mechanism; the present invention can prevent the texture of solid food from being damaged and can more homogeneously and finely agitate the mushy food. The present invention can improve the agitation results of the agitating mechanism. At low speed, the agitating mechanism can perform the agitation gently without damaging the texture of the solid food. At high speed, the agitating mechanism can more homogeneously and finely agitate the mushy food with enhanced agitating efficiency.

FIG. 1 through FIG. 6 are flow charts of control methods according to various embodiments of the present invention.

FIG. 7 through FIG. 9 are diagram of control system according to various embodiments of the present invention.

Below, embodiments of the present invention will be described in greater detail with reference to the drawings.

Referring to FIG. 1 through FIG. 6 , the present invention provides a control method for an agitating mechanism. The main technical solution of the control method includes:

step s 1 which is an electrical current obtaining step of receiving a load current detected by a current detecting apparatus when the agitating mechanism is rotating along a specific direction;

step s 2 which is a trigger determination step of determining whether the rotation of the agitating mechanism meets a preset trigger condition based on the load current; and

step s 3 which is a rotation control step of controlling the agitating mechanism to rotate in a direction opposite from the specific direction when the trigger condition is met.

Several embodiments of the control method of the present invention will be described below based on the above main technical solution.

Based on the above main technical solution, the present invention provides the following first to fourth embodiments to deal with the situation that the rotation of the agitating mechanism is jammed.

In the first embodiment of the control method of the present invention, whether jam occurs is determined based on the load current. Referring to FIG. 3 , in this embodiment, the trigger determination step s 2 includes a trigger judgment step s 21 which refers in particular to jam determination in which whether the rotation of the agitating mechanism meets the trigger condition is determined directly based on the load current. The trigger condition is that the load current is continuously greater than a preset first current threshold within a preset first time duration.

In the second embodiment of the control method of the present invention, whether jam occurs is determined based on a load torque. Referring to FIG. 4 , in this embodiment, the trigger determination step s 2 includes:

a torque calculation step s 22 of calculating the load torque based on the load current; and

a trigger judgment step s 23 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load torque, wherein the trigger condition is that the load torque is continuously greater than a preset first torque threshold within a preset third time duration, and wherein the first torque threshold is less than a rated maximum output torque of the agitating mechanism.

In the third embodiment of the control method of the present invention, whether jam occurs is determined based on the load current and a rotation speed of the agitating mechanism. Referring to FIG. 5 , in addition to the above main technical solution, this embodiment further includes:

a speed obtaining step s 20 of receiving a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus;

the trigger determination step s 2 including a trigger judgment step s 24 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load current and the rotation speed, wherein the trigger condition is that the load current is continuously greater than a preset third current threshold within a preset fifth time duration and the rotation speed is continuously less than a preset first rotation speed threshold within a preset sixth time duration.

In the fourth embodiment of the control method of the present invention, whether jam occurs is determined also based on the load torque. Referring to FIG. 6 , in addition to the above main technical solution, this embodiment further includes:

a speed obtaining step s 20 of receiving a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus;

the trigger determination step s 2 including:

a torque calculation step s 25 of calculating the load torque based on the load current and the rotation speed; and

a trigger judgment step s 26 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load torque, wherein the trigger condition is that the load torque is continuously greater than a preset third torque threshold within a preset ninth time duration, and wherein the third torque threshold is less than the rated maximum output torque of the agitating mechanism.

Based on the above main technical solution, the present invention provides the following fifth to eighth embodiments to deal with the situation that the cavity is formed in the viscous food due to the blocking of the high rotation speed agitating mechanism.

In the fifth embodiment of the control method of the present invention, whether a cavity is formed is determined based on the load current. Referring to FIG. 3 , in this embodiment, the trigger determination step s 2 includes a trigger judgment step s 21 which refers in particular to cavity determination in which whether the rotation of the agitating mechanism meets the trigger condition based on the load current. The trigger condition is that the load current is continuously less than a preset second current threshold within a preset second time duration.

In the sixth embodiment of the control method of the present invention, whether the cavity is formed is determined based on a load torque. Referring to FIG. 4 , in this embodiment, the trigger determination step s 2 includes:

a torque calculation step s 22 of calculating the load torque based on the load current; and

a trigger judgment step s 23 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load torque, wherein the trigger condition is that the load torque is continuously less than a preset second torque threshold within a preset fourth time duration.

For example, for a motor-driven agitating mechanism, the load torque is approximately equal to an electromagnetic torque when the load is balanced. In the torque calculating step, the electromagnetic torque may be calculated according to motor parameters, which is then used to estimate the load torque.

Firstly, the electromagnetic torque is calculated according to the formula T em =3/2*P n *(ψ f *i d +(L d −L q )*i d *i q ).

The load torque T em ≈T load , the load torque can therefore be estimated according to the formula T load =3/2*P n *(ψ f *i d +(L d −L q )*i d *i q ),

where:

T em is the electromagnetic torque, T load is the load torque;

i d is the detected d-axis current, i q is the detected q-axis current;

Ψ f is the magnetic linkage, L d is the d-axis inductance, L q is the q-axis inductance, P n is the number of pole pairs of the motor, all of which are pre-obtained and can be preset.

In the seventh embodiment of the control method of the present invention, whether a cavity is formed is determined based on the load current and a rotation speed of the agitating mechanism. Referring to FIG. 5 , in addition to the above main technical solution, this embodiment further includes:

a speed obtaining step s 20 of receiving a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus;

the trigger determination step s 2 including a trigger judgment step s 24 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load current and the rotation speed, wherein the trigger condition is that the load current is continuously greater than a preset fourth current threshold within a preset seventh time duration and the rotation speed is continuously greater than a preset second rotation speed threshold within a preset eighth time duration.

In the eighth embodiment of the control method of the present invention, whether a cavity is formed is determined based on the load torque. Referring to FIG. 6 , in addition to the above main technical solution, this embodiment further includes:

a speed obtaining step s 20 of receiving a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus;

the trigger determination step s 2 including:

a torque calculation step s 25 of calculating the load torque based on the load current and the rotation speed; and

a trigger judgment step s 26 of determining whether the rotation of the agitating mechanism meets the trigger condition based on the load torque, wherein the trigger condition is that the load torque is continuously less than a preset fourth torque threshold within a preset tenth time duration.

For example, for the motor-driven agitating mechanism, by analyzing motor load characteristics, a load torque calculation table can be generated using finite-element analysis. In addition, Loss of machine necessarily occur in a motor during operation. Loss of machine mainly include iron losses and copper losses. Furthermore, temperature variations also affect the accuracy of the load torque. Therefore, in generating the table with this method, Loss of machine and temperature variations should be taken into account. As such, the torque calculating step is performed as follows: according to the detected load current i d and i q , the detected rotation speed ω r , and preset motor losses P fe and temperature T, the corresponding load torque is looked up in the preset torque lookup table. This method is equally applicable in the load torque calculation of the above fourth embodiment.

The above first to fourth embodiments are specially provided for the jam situation, and the fifth to eighth embodiment are specially provided for the cavity situation. In fact, a ninth embodiment can be provided for trigger in response to the jam as well as the cavity. For example, a ninth embodiment may be obtained by combining the first embodiment and the fifth embodiment, or by combining the second embodiment and the sixth embodiment, or by combining the third embodiment and the seventh embodiment, or by combining the fourth embodiment and the eight embodiment.

In the rotation control step S 3 of the control method of the present invention, after the direction is reversed, the agitating mechanism can be controlled to keep the rotation direction until the next time the trigger condition is met. As such, the texture of the agitated solid content is not damaged, and the mushy content is made more homogeneous.

Preferably, the agitating blades of the agitating mechanism of the present invention can be configured as double-edged agitating blades rather than the ordinary agitating blades which have a single-sided cutting edge. Rotation of the double-edged agitating blades in either direction can cut and agitate the food, and can achieve better agitating results under the automatic direction reverse control of the present invention.

The present invention further provides a ninth embodiment of the control method based on any one of the above first to e embodiment. Further, as shown in FIG. 1 , the rotation control step s 3 includes:

a first reverse rotation step s 31 of controlling the agitating mechanism to rotate reversely when the trigger condition is met;

a further reverse determination step s 32 a of determining whether the rotation of the agitating mechanism in the reversed direction has lasted a preset eleventh time duration from the moment the agitating mechanism starts the reverse rotation; and a second reverse step s 33 of controlling the agitating mechanism to rotate reversely again if the determining result of step s 32 a is yes.

It should be understood that, in step s 32 a , if it is determined that the trigger condition is met before the preset eleventh time duration of the continuous rotation in the reverse direction ends, the method proceeds to perform step s 31 .

Similar to the ninth embodiment, the present invention further provides an eleventh embodiment of the control method based on any one of the above first to ninth embodiments. Further, as shown in FIG. 2 , the rotation control step includes:

a first reverse rotation step s 31 of controlling the agitating mechanism to rotate reversely when the trigger condition is met;

a further reverse determination step s 32 b of determining whether the angle the agitating mechanism rotates over in the reversed direction has reached a preset first angle from the moment the agitating mechanism starts the reverse rotation; and

a second further reverse step s 33 of controlling the agitating mechanism to rotate reversely again if the determining result of step s 32 b is yes.

It should be understood that, in step s 32 b , if it is determined that the trigger condition is met before the rotation angle in the reversed direction reaches the preset first angle, the method proceeds to perform step s 31 .

In the tenth embodiment and eleventh embodiment, after reversed, the agitating mechanism maintains the reverse rotation for a short time duration before automatic direction reverse again. That is, the agitating mechanism retreats a small step and then continues to advance in the initial rotating direction. By means of a space made by the retreat of the agitating mechanism, or by means of the space and the flow of substance as a result of the space, the position of the resisting block or the cavity is changed, and then the normal agitation continues. This can to some extent address the issue that the solid content's texture is damaged or the cavity resides in the mushy content. This control manner is more suitable for agitating mechanism with single-edged agitating blades, without the need of modifying the outer profile of the agitating blades.

The control system has multiple embodiments corresponding to the multiple embodiments of the control method. Based on the disclosure of the present invention, embodiments of the corresponding control system can be determined uniquely and unambiguously, and illuminated in drawings 7 - 9 , respectively.

The control system in these embodiments includes an electrical current obtaining module M 1 configured to receive a load current detected by a current detecting apparatus when the agitating mechanism is rotating along a specific direction, i.e. to fulfill the electrical current obtaining step s 1 in the control method, a trigger determination module M 2 configured to determine whether the rotation of the agitating mechanism meets a preset trigger condition based on the load current, i.e. to fulfill the trigger determination step s 2 in the control method, and a rotation control module M 3 configured to control the agitating mechanism to rotate in a direction opposite from the specific direction when the trigger condition is met, i.e. fulfill the rotation control step s 3 in the control method. The trigger determination module M 2 of the control system in some embodiments includes a torque calculation unit M 22 configured to calculate a load torque based on the load current and a trigger judgment unit M 23 configured to determine whether the rotation of the agitating mechanism meets the trigger condition based on the load torque. The control system in some embodiments further includes a speed obtaining module M 20 configured to receive a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus, the trigger determination module M 2 thereof configured to determine whether the rotation of the agitating mechanism meets a preset trigger condition based on both the load current and the rotation speed of the agitating mechanism. The trigger determination module M 2 of the control system in some embodiments includes a torque calculation unit M 25 configured to calculate a load torque based on the load current and the rotation speed the agitating mechanism.

The rotation control module M 3 of the control system in some embodiments includes a first reverse rotation unit M 31 configured to control the agitating mechanism to rotate reversely when the trigger condition is met, a further reverse determination unit M 32 configured to determine whether the rotation of the agitating mechanism in the reversed direction has lasted a preset eleventh time duration from the moment the agitating mechanism starts the reverse rotation, or determining whether an angle the agitating mechanism rotates over in the reversed direction has reached a preset first angle from the moment the agitating mechanism starts the reverse rotation, and a second reverse unit M 33 configured to control the agitating mechanism to rotate reversely again if the determining result of the further reverse determination unit is yes.

The control system in some embodiments further includes a speed obtaining module M 20 configured to receive a rotation speed of the agitating mechanism that is detected by a speed detecting apparatus.

Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.