DE102018200784A1 - Transport device, in particular stroller with mass estimate - Google Patents

Abstract

In a transport device (100), in particular a stroller, with at least three wheels (116, 118, 120, 122) and with a handle (110) for a user, wherein of the at least three wheels at least one wheel (120, 122) as Drive wheel (132, 134) is formed, which is driven by an associated electric drive unit (140, 142) by an electric motor to allow at least partially electromotive assistance of a manual sliding or pulling operation of the transport device by the user, and wherein the electric drive unit means one of these associated torque control device (200, 202) is controllable and the transport device has a computing unit (400) for mass estimation of the transport device, at least one acceleration sensor (170, 172) is provided and the torque control device (200, 202) is connected to a test signal (Ts) acted upon, wherein the arithmetic unit (400) is adapted to beind est on the basis of the test signal (T) on the transport device (100) and generated by the at least one acceleration sensor (172) detected acceleration signal (y (t)) to determine a mass (m) of the transport device (100).

Description

State of the art

The present invention relates to a transport device, in particular a stroller, with at least three wheels and a handle for a user, wherein of the at least three wheels at least one wheel is designed as a drive wheel, which is driven by an electric motor driven electric motor to at least one partially to enable electromotive support manual sliding or pulling operation of the transport device by the user, and wherein the electric drive unit by means of one of these associated torque control device is controllable and the transport device has a computing unit for mass estimation of the transport device. In addition, the invention has a method for estimating a mass of a transport device, in particular a baby carriage, the subject.

From the prior art trained as a stroller transport devices with an active support of a user in the sliding or pulling operation by an electric motor drivable drive wheel are known. In order to achieve optimal support results, in particular for user and load regulation of generally at least one electric motor driven drive wheel of a rear axle of the stroller, in addition to the exact knowledge of the type of substrate on which the stroller is moved, the knowledge of the current mass of the stroller central.

However, the mass of a baby carriage is variable, inter alia due to varying equipment components or accessories and / or the weight of at least one child to be included therein. In addition, the detection of the complete mass of the stroller including the wheels is complicated if a weight measurement, for example, with the aid of several strain gauges, spring elements or the like should be used to detect slight weight-dependent deformations of the chassis of the stroller and their transformation in weight or Mass-proportional electrical measurement signals are required. Furthermore, a direct mass measurement by force sensors on all the wheel axles of the baby carriage is not only complicated with regard to the necessary wiring or possibly wireless data transmission.

Disclosure of the invention

The present invention relates to a transport device, in particular a stroller with at least three wheels and with a handle for a user, wherein of the at least three wheels at least one wheel is designed as a drive wheel which is driven by an electric motor drive unit by an electric motor, at least partially allow electromotive assistance of a manual sliding or pulling operation of the transport device by the user. The electric drive unit can be controlled by means of a torque control device associated therewith, and the transport device has an arithmetic unit for mass estimation of the transport device. At least one acceleration sensor is provided and the torque control device can be acted upon by a test signal, wherein the arithmetic unit is designed to determine a mass of the transport device based at least on the acceleration signal generated by the test signal on the transport device and detected by the at least one acceleration sensor.

As a result, a comparatively precise detection of a (total) mass of the transport device in real time or "online" possible. In the context of this description, the mass is understood to mean the mass of the transport device, including all accessories and add-on parts, as well as the weight of at least one object or child to be transported by means of the transport device. An otherwise necessary placement of a plurality of weight sensors at different positions on the chassis of the transport device can be omitted.

According to a preferred embodiment, the test signal is a sinusoidal or cosinusoidal torque signal. Due to the harmonic waveform simplify the required mathematical and numerical effort in the mass calculation of the transport device considerably.

The electric drive unit preferably has an electric motor, in particular a brushless DC motor. As a result, a practically low-wear, substantially low maintenance and excellent controllable drive the transport device is guaranteed.

Preferably, the electric drive unit is associated with a transmission. As a result, a flexible torque adjustment of the electric motors to the requirements of the transport device is possible. Optionally, a gear change can be provided with at least one gear to, for example, in addition to a flat-land operation also allow a mining operation of the transport device.

In a further technically advantageous embodiment, by means of the at least one acceleration sensor substantially an acceleration signal in a primary sliding or pulling direction of the transport device can be detected. As a result, a main movement direction of the transport device for mass estimation is primarily used.

According to a further advantageous embodiment, the mass of the transport device can be estimated by means of a frequency analysis implemented by the arithmetic unit. In this connection, various numerical methods, such as a discrete Fourier transform, can be used to calculate the mass.

Preferably, the arithmetic unit for frequency analysis on a Goertzel filter. As a result, a particularly effective numerical evaluation for mass estimation is given.

According to a technically advantageous development, the arithmetic unit has a correlator for estimating the mass of the transport device. As a result, a tried-and-tested evaluation method based on news and radio technology is available.

The estimation of the mass by means of the arithmetic unit preferably takes place in real time. As a result, a very comfortable control of the electrically assisted sliding and pulling operation of the transport device is possible in each case depending on the current circumstances.

According to one embodiment, of the at least three wheels, at least two wheels are designed as drive wheels, each of which can be driven by an electric drive unit by means of at least one electric drive unit, and wherein the electric drive units can be controlled independently of one another by means of a respectively associated torque control device. Thus, a symmetrical drive of the transport device can be made possible, in which a so-called "skewing" in the sliding or pulling operation of the transport device can be avoided.

Moreover, the present invention provides a method for estimating a mass of a transport device, in particular a stroller, with at least three wheels and with a handle for a user. Of the at least three wheels, at least one wheel can be driven as an electric motor by means of an electric drive unit to ensure at least partial electromotive support of a manual sliding or pulling operation of the transport device by the user, wherein the electric drive unit is controllable by means of a torque control device associated therewith. The torque control device is subjected to a test signal for vibrational excitation of the transport device and an estimate of the mass of the transport device takes place at least by evaluating the acceleration signal detected by at least one acceleration sensor.

As a result, a comparatively accurate detection of a current (total) mass of the transport device without the need for placement of a plurality of weight sensors on the transport device in real time is possible.

In a favorable development of the method, the evaluation takes place by means of a Goertzel algorithm implemented with the aid of a computing unit. This ensures a numerically resource-saving or mathematically effective numerical conversion by means of the arithmetic unit.

In the case of a further embodiment, the evaluation takes place by means of a correlation implemented with the aid of a computing unit. As a result, it is possible to fall back on the proven and proven correlation method, which has long been tried and tested in particular in the news and radio technology.

list of figures

• 1 eine schematische Seitenansicht einer als Kinderwagen ausgebildeten Transportvorrichtung,
• 2 ein mechanisch-elektrisches Blockdiagramm des Kinderwagens von 1 mit einer Recheneinheit zur Masseabschätzung,
• 3 ein schematisches Blockschaltbild des Kinderwagens von 1 mit einem mittels der Recheneinheit implementierten Goertzel-Filter, und
• 4 ein schematisches Blockschaltbild des Kinderwagens von 1 mit einem mittels der Recheneinheit implementierten Korrelator.

The invention is explained in more detail in the following description with reference to exemplary embodiments illustrated in the drawings. Show it:

• 1 a schematic side view of a transport device designed as a stroller,
• 2 a mechanical-electrical block diagram of the stroller of 1 with an arithmetic unit for mass estimation,
• 3 a schematic block diagram of the stroller of 1 with a implemented by means of the arithmetic unit Goertzel filter, and
• 4 a schematic block diagram of the stroller of 1 with a correlator implemented by means of the arithmetic unit.

Description of the embodiments

1 shows a transport device 100 according to the invention with integrated mass estimation. Illustrative and exemplary is the transport device 100 designed as a stroller and is hereinafter referred to as "stroller 100".

It should be noted that the design of the transport device 100 as a stroller has only exemplary character and is not to be understood as limiting the invention. So the transport device 100 also be designed in the manner of any other transport device having a mass estimate, for example in the manner of a wheelbarrow, a sack truck, a garbage can. The stroller 100 preferably has a preferably collapsible chassis 102 with a couch or seat pan 104 , In this is preferably a mattress 106 as a support for at least one child 108 inserted.

On the chassis 102 is preferably a handle 110 arranged for a user, not shown, for example, an ergonomically height-adjustable, U-shaped handle. The stroller 100 is due to the action of a user Fu on the U-shaped handle 110 automatically displaced into an electrically at most partially assisted pushing or pulling operation, whereby the stroller 100 essentially in a sliding or pulling direction 112 on a surface 114 emotional.

The stroller 100 with an estimated or with a sufficient accuracy to be determined (total) mass m _K Here is an example of four wheels 116 . 118 . 120 . 122 of which only the front wheels in relation to the plane of the drawing 116 . 120 are shown graphically. Alternatively, the stroller 100 also be three-wheeled with a front wheel and with two preferably electromotively driven rear wheels. Preferably, the stroller 100 at least three wheels 116 . 118 . 120 . 122 on. Preferably, two wheels are on a rear axle 130 and a wheel on a front axle 128 arranged, however, can also have two wheels on the front axle 128 and a wheel on the rear axle 130 be arranged. The crowd m _K of the baby carriage 100 results in a weight force F _g , which are perpendicular in the direction of the here only exemplary plan underground 114 acts, with a value of the gravitational acceleration g of about 9.81 m / s ^{2 is} assumed.

The two rear wheels 120 . 122 are here merely exemplary than with the aid of an electric drive unit 140 . 142 individually driven by electric motor drive wheels 132 . 134 executed. From the two drive wheels 132 . 134 again is only the first drive wheel in relation to the plane of the drawing 132 can be represented graphically. The first drive wheel 132 is by means of the first electric drive unit 140 and the second drive wheel 134 is by means of the second electric drive unit 142 independent of the first drive wheel 132 drivable. Of the at least three wheels 116 . 118 . 120 . 122 is preferably at least one wheel 120 . 122 as a drive wheel 132 . 134 educated. The at least one drive wheel 132 . 134 is preferably by means of at least one electric drive unit 140 . 142 can be driven by an electric motor. This can be at least one drive wheel 132 . 134 at the front axle 128 and / or the rear axle 130 be arranged.

The two electric drive units 140 . 142 are preferred to at most partially electromotive support the push and pull operation of the baby carriage 100 in the simplest case, each with an electric motor 150 . 152 realized. The first electric motor 150 is preferably a first transmission 158 and the second electric motor 152 is accordingly a second transmission 160 downstream of the torque adjustment.

In addition, the two electric drive units 140 . 142 with mechanical clutches for force flow interruption, with mechanical brakes to support electromotive deceleration of the stroller 100 through the electric drive units 140 . 142 and equipped with locking devices. Preferably, the two electric motors 150 . 152 To ensure optimum controllability with a permanent magnet synchronous machine or a brushless DC motor (sg "brushless DC motor") realized. For the two gears 158 . 160 Especially planetary gear due to their compact design and the achievable high transmission and reduction ratios into consideration. The electric drive units 140 . 142 or the electric motors 150 . 152 with the respective downstream gearboxes 158 . 160 are with the better graphic overview half not designated hubs of the drive wheels 132 . 134 of the baby carriage 100 rotatably connected.

Every electric drive unit 140 . 142 is preferably a respective torque control device 200 . 202 assigned. In the electromotive at most partially assisted push and pull operation of the stroller 100 there are speed changes .DELTA.v , which in turn leads to accelerations a _z perpendicular to the ground 114 This process is similar to "dipping" when accelerating or "lifting" the stern when decelerating a rear-wheel drive motor vehicle. The orientation of the acceleration a _z as well as an acceleration a _y in the primary pushing or pulling direction of the baby carriage 100 in space is through a coordinate system 199 illustrated.

Furthermore, the stroller has 100 for the indirect estimation of the mass according to the invention m _K by means of a computing unit 400 preferably via at least a first and a second acceleration sensor 170 . 172 , The two acceleration sensors 170 . 172 serve to prioritize the acceleration a _y , in the normal pushing or pulling operation of the baby carriage 100 occur. The acceleration sensors 170 . 172 can in the electric drive units 140 . 142 the two drive wheels 132 . 134 be integrated.

2 illustrates a mechanical-electrical block diagram of the baby carriage 100 from 1 with the two torque control devices 200 . 202 wherein the first torque control device 200 with the first electric drive unit 140 connected is. Accordingly, the second torque control device 202 with the second electric drive unit 142 coupled. The first electric drive unit 140 includes the first electric motor 150 , the first gearbox 158 is downstream. Corresponding to this, the structural design of the second electric drive unit designed 142 that the second electric motor 152 with the subsequent second transmission 160 having. The first electric drive unit 140 is with the first drive wheel 132 of the baby carriage 100 coupled while the second electric drive unit 142 rotatably with the second drive wheel 134 of the baby carriage 100 connected is. On the two drive wheels 132 . 134 of the baby carriage 100 act primarily by means of the two electric drive units 140 . 142 generated mechanical driving forces F _W1 such as F _W2 on.

According to the invention, the two torque control devices 200 . 202 with a merely exemplary sinusoidal or cosinusoidal test signal T _S acted or controlled. Other periodic waveforms, such as trapezoidal, triangular, rectangular, or aperiodic, irregular waveforms, are also possible. Alternatively or additionally, an application of the torque control devices 200 . 202 possible with different test signals. Due to the here only exemplary and preferably periodic-temporary excitation of the torque control devices 200 . 202 with the here sinusoidal or cosinusoidal test signal T _S follows a time-varying or harmonious oscillating course of the drive wheels 132 . 134 upcoming drive forces F _W1,2 ,

At a first and a second node 210 . 212 an overlay of the electric drive units takes place 140 . 142 generated driving forces F _W1,2 with other forces occurring in the stroller operation, such as the user Fu, preferably divided into two on both sides of the handle 110 from 1 of the baby carriage 100 attacking users F _U1,2 , on the wheels of the stroller 100 acting frictional forces F _R1,2 as well as other external forces F _ext.1,2 , wherein the above-mentioned forces at the same time as well as in their effect complement each other to one here the entirety of the baby carriage 100 representing or imaging control loop 230 act. At the external forces F _ext1,2 it can be, for example, wind loads, force effects by a stroller 100 leashed pet, another child carried by a trailer roll board, downhill forces, or the like.

A first and a second output signal 214 . 216 of the two nodes 210 . 212 is preferred to the entirety of the baby carriage 100 representing control loop 230 supplied, wherein the first output signal 214 in the case of a substantially pure sinusoidal or cosinusoidal test signal Ts one in the control loop 230 incoming torque signal u ₁ (t) in accordance with the equation u ₁ (t) = u ₀ sin (ωt) and the second output signal 216 one in the control loop 230 fed torque signal u ₂ (t) according to the equation u ₂ (t) = u ₀ sin (ωt).

The stroller 100 is preferably by means of the control of the two torque control devices 200 . 202 with the preferred harmonic test signal Ts generated two torque curves u _1,2 (t) = u ₀ sin (ωt), or the output signals 214 . 216 behind the two nodes 210 . 212 , excited to corresponding mechanical (eigen) vibrations. The resulting accelerations of the baby carriage 100 are preferably with the help of at least two, in a suitable manner to the stroller 100 positioned acceleration sensors 170 . 172 measured.

The of the two acceleration sensors 170 . 172 due to the stimulation of the baby carriage 100 by means of the preferably sinusoidal or cosinusoidal test signal Ts output acceleration signals 220 . 222 In this case, the equation y ₁ (t) = y ₀ sin (ωt + φ) and the equation y ₂ (t) = y ₀ sin (ωt + φ), wherein the phase shift φ in the equations in each case by the action of the control loop 230 results. The of the two acceleration sensors 170 . 172 determined acceleration signals 220 . 222 are then preferably a preferably digital electronic processing unit 400 to estimate or calculate the sought mass m _K supplied to the stroller.

3 Illustrates a schematic block diagram of the baby carriage 100 from 1 with one by means of the arithmetic unit 400 implemented Goertzel filter 250 , The control loop 230 is preferred by the with the help of only exemplary sinusoidal or cosinusoidal test signal T _S generated output signals 214 . 216 which, in the case of the sinusoidal or cosinusoidal excitation given here, obey the equation u _1,2 (t) = u ₀ sin (ωt), can be excited to corresponding mechanical vibrations due to the physical conditions of the entirety of the baby carriage 100 imaging loop 230 to by means of the acceleration sensors (see. 2 , Reference numbers 170 . 172 ) lead to easily measurable mechanical accelerations. These accelerations, the temporal course of which in the constellation described here obeys at least approximately the equation y _1,2 (t) = y ₀ sin (ωt + φ), are determined by the at least two acceleration sensors (see in particular FIG. 2 , Reference numbers 170 . 172 ) and as acceleration signals 220 . 222 to the arithmetic unit 400 transmitted for further evaluation.

With the help of the arithmetic unit 400 is also a digital Goertzel filter 250 realized on the basis of the so-called Goertzel algorithm, which has a maximum acceleration value 252 or a discrete maximum acceleration value y ₀ supplies. The Goertzel algorithm is sufficiently familiar to a person skilled in the art of control engineering, so that at this point, for the sake of brevity of the description, a more detailed explanation of the mathematical specificity of the Goertzel algorithm is dispensed with.

die abzuschätzende (Gesamt-)Masse m_K des Kinderwagens ermittelbar, denn es gelten die weiteren Gleichungen F = m * α sowie der Drehmomentgleichung M = F * s, woraus sich durch einfaches Umformen und Einsetzen die Gleichung zur Masseträgheit $m=\frac{M}{a\ast s}$

zur Ermittlung der Masse ergibt.From the maximum acceleration value y ₀ is along with the known maximum torque value u ₀ in another processing stage 254 the arithmetic unit 300 preferably according to the formula $m_k=\frac{u_0}{y_0}$

the estimated (total) mass m _K of the baby carriage can be determined, because the additional equations F = m * α and the torque equation M = F * s apply, from which the equation for inertia of mass is obtained by simple deformation and insertion $m=\frac{M}{a*s}$

to determine the mass results.

The Goertzel algorithm or the technically implemented Goertzel filter 250 allows a sufficiently accurate determination or estimate of the mass as compared to other known frequency analysis techniques, such as the discrete Fourier transform m _K of the baby carriage 100 at the same time still acceptable, by the arithmetic unit 400 still to be handled numerical or mathematical effort for real-time or online determination of the mass m _K of the baby carriage 100 ,

4 shows a schematic block diagram of the baby carriage 100 from 1 with one by means of the arithmetic unit 400 from 1 implemented correlator 350 , By means of the test signal T _S acted upon, also not shown here torque control devices 200 . 202 from 1 is the stroller 100 again representing control loop 230 with first torque signals 300 can be excited according to the relationship u _1,2 (t) = u ₀ sin (ωt), from which the output side first acceleration signals 302 according to the equation y _1.2 = y ₀ sin (ωt + φ). Further, by means of the test signal Ts in the same way phase-shifted second torque signals 304 in accordance with the equation u _1,2 (t) = u ₀ cos (ωt) generated which, however, about 90 ° out of phase with the first torque signals 300 are.

To determine the (total) mass m _K of the baby carriage 100 indicates the arithmetic unit 400 preferably different from the Goertzel filter of 3 here a correlator 350 on, the example with a first and a second multiplier 352 . 354 and a first and a second averager 356 . 358 is constructed. The first averager 356 is the first multiplier 352 downstream and the second averager 358 is the second multiplier 354 downstream.

The first torque signals 300 preferably effect after passing through the control loop 230 first acceleration signals 302 in accordance with the equation y _1,2 (t) = y ₀ sin (ωt + φ), which the two multipliers 352 . 354 of the correlator 350 be fed in parallel. Furthermore, the first torque signals 300 preferably the first multiplier 352 and the phase-shifted, second torque signals 304 the second multiplier 354 fed. A product 360 of the first multiplier 352 arrives at the first averager 356 while a product 362 of the second multiplier 354 the second averager 358 is supplied.

des zweiten Mittelwertbildners 358, wobei die Variable T_P jeweils einer konstanten Periodenzeit entspricht, lässt sich bevorzugt anhand der nachfolgend angegebenen Formeln (1) bis (5) mittels der Recheneinheit 400 die zu schätzende bzw. hinreichend genau zu ermittelnde Masse m_K des Kinderwagens 100 ableiten: $${\varnothing }_{uy}\left(0\right)=\frac{1}{n{T}_p}{\displaystyle \underset{0}{\overset{n{T}_p}{\int }}{u}_0\text{ cos}\left(\omega t+\phi \right)}{y}_0\text{ sin}\left(\omega t+\phi \right)dt$$

$$-{\varnothing }_{uy}\left(\frac{T_p}{4}\right)=-\frac{1}{n{T}_p}{\displaystyle \underset{0}{\overset{n{T}_p}{\int }}{u}_0\text{ cos}\left(\omega t+\phi \right)}{y}_0\text{ sin}\left(\omega t+\phi \right)dt$$

$${\varnothing }_{uy}\left(\frac{T_p}{4}\right)=\frac{y_0}{u_0}\frac{u_0^2}{2}\text{cos}\phi$$

$${\varnothing }_{uy}\left(\frac{T_p}{4}\right)=\frac{y_0}{u_0}\frac{u_0^2}{2}\text{sin}\phi$$

$$\left|G\left(i\omega \right)\right|=\sqrt{{\left(\frac{y_0}{u_0}\text{sin}\left(\phi \right)\right)}^2+{\left(\frac{y_0}{u_0}\text{cos}\left(\phi \right)\right)}^2}=\frac{y_0}{u_0}=\frac{1}{m_K}$$

Starting from the correlated output Ø _{uy of} the first averager 356 and the correlated output signal $-{\varnothing }_{uy}\left(\frac{T_P}{4}\right)$

of the second averager 358 , where the variable T _P each corresponds to a constant period, can be preferably based on the following formulas (1) to (5) by means of the arithmetic unit 400 the mass to be estimated or sufficiently accurately determined m _K of the baby carriage 100 derived: $${\varnothing }_{uy}\left(0\right)=\frac{1}{n{T}_p}{\displaystyle \underset{0}{\overset{n{T}_p}{\int }}{u}_0\text{cos}\left(\omega t+\phi \right)}{y}_0\text{sin}\left(\omega t+\phi \right)dt$$

$$-{\varnothing }_{uy}\left(\frac{T_p}{4}\right)=-\frac{1}{n{T}_p}{\displaystyle \underset{0}{\overset{n{T}_p}{\int }}{u}_0\text{cos}\left(\omega t+\phi \right)}{y}_0\text{sin}\left(\omega t+\phi \right)dt$$

$${\varnothing }_{uy}\left(\frac{T_p}{4}\right)=\frac{y_0}{u_0}\frac{u_0^2}{2}\text{cos}\phi$$

$${\varnothing }_{uy}\left(\frac{T_p}{4}\right)=\frac{y_0}{u_0}\frac{u_0^2}{2}\text{sin}\phi$$

$$\left|G\left(i\omega \right)\right|=\sqrt{{\left(\frac{y_0}{u_0}\text{sin}\left(\phi \right)\right)}^2+{\left(\frac{y_0}{u_0}\text{cos}\left(\phi \right)\right)}^2}=\frac{y_0}{u_0}=\frac{1}{m_K}$$

With the help of the digital processing unit 400 technically implemented correlator 350 is therefore an estimate or determination of the mass m _K of the baby carriage 100 with the help of known inter alia from telecommunications and proven correlation method possible, which is well known to those working in the field of control engineering expert.

In a method according to the invention for estimating the mass m _K the example designed as a stroller transport device are preferably initially the torque control devices 200 . 202 from 1 with the test signal T _S for the mechanical vibration excitation of the baby carriage 100 from 1 applied. An estimate of the crowd m _K of the baby carriage 100 takes place at least by evaluating the at least one acceleration sensor 170 . 172 from 1 detected acceleration signal y _1,2 (t) , However, also an estimate of the mass m _K of the baby carriage 100 at least by evaluating the at least two acceleration sensors 170 . 172 from 1 recorded acceleration signals y _1,2 (t) respectively. The determination or estimation of the mass m _K of the baby carriage 100 is done either by the so-called Goertzel algorithm or by a correlation each with the help of the digital electronic processing unit 400 from 1 ,

Alternatively, on the stroller 100 from 1 a plurality of further acceleration sensors may be provided, the accelerations in one of the primary pushing and pulling direction of the baby carriage 100 detect deviating direction. Furthermore, it is also possible to provide sensors for measuring rotational accelerations about all axes of the room.

Claims (13)

Transport device (100), in particular stroller, with at least three wheels (116, 118, 120, 122) and with a handle (110) for a user, wherein of the at least three wheels (116, 118, 120, 122) at least one wheel (120, 122) as a drive wheel (132, 134) is formed, which is driven by an associated electric drive unit (140, 142) by an electric motor to an at least partially electromotive support a manual sliding or pulling operation of the transport device (100) by the user and wherein the electric drive unit (140, 142) is controllable by means of a torque control device (200, 202) associated therewith, and the transport device (100) has an arithmetic unit (400) for mass estimation of the transport device (100), characterized in that at least an acceleration sensor (170, 172) is provided and the torque control device (200, 202) acted upon by a test signal (T _S ) r is, wherein the arithmetic unit (400) is designed, at least on the basis of the acceleration signal (y _1,2 (t)) generated by the test signal (T _S ) on the transport device (100) and detected by the at least one acceleration sensor (172) to determine a mass (m _K ) of the transport device (100). Transport device after Claim 1 , characterized in that the test signal (T _S ) is a sinusoidal or cosinusoidal torque signal (u _1,2 (t)). Transport device after Claim 1 or 2 , characterized in that the one electric drive unit (140, 142) comprises an electric motor (150, 152), in particular a brushless DC motor. Transport device according to one of the preceding claims, characterized in that the one electric drive unit (140, 142) is associated with a transmission (158, 160). Transport device after Claim 4 , characterized in that by means of the at least one acceleration sensor (170, 172) substantially an acceleration signal (y _1,2 (t)) in a primary sliding or pulling direction (112) of the transport device (100) can be detected. Transport device according to one of the preceding claims, characterized in that the mass (m _K ) of the transport device (100) can be estimated by means of a frequency analysis implemented by the arithmetic unit (400). Transport device after Claim 6 , characterized in that the arithmetic unit (400) for frequency analysis comprises a Goertzel filter (250). Transport device after Claim 7 , characterized in that the arithmetic unit (400) comprises a correlator (350) for estimating the mass (m _K ) of the transport device (100). Transport device according to one of the preceding claims, characterized in that the estimation of the mass (m _K ) by means of the computing unit (400) takes place in real time. Transport device according to one of the preceding claims, characterized in that of the at least three wheels (116, 118, 120, 122) at least two wheels (120, 122) as drive wheels (132, 134) are formed, each by means of at least one electric drive unit (140, 142) can be driven by an electric motor, and wherein the electric drive units (140, 142) are independently controllable by means of a respectively associated torque control device (200, 202). Method for estimating a mass (m _K ) of a transport device (100), in particular a pushchair, having at least three wheels (116, 118, 120, 122) and a handle (110) for a user, wherein of the at least three wheels ( 116, 118, 120, 122) at least one wheel (120, 122) as a drive wheel (132, 134) by means of an electric drive unit (140, 142) is driven by an electric motor to at least partially electromotive support a manual sliding or pulling operation of the transport device (100) to be ensured by the user, wherein the electric drive unit (140, 142) by means of an associated torque control device (200, 202) is controllable, characterized in that the torque control device (200, 202) with a test signal (T _S ) for vibrational Excitation of the transport device (100) is acted upon and an estimate of the mass (m _K ) of the transport device (100) at least by evaluating the acceleration signal (y _1,2 (t)) detected by at least one acceleration sensor (170, 172). Method according to Claim 11 , characterized in that the evaluation is carried out by means of a computing unit (400) implemented Goertzel algorithm. Method according to Claim 11 , characterized in that the evaluation is carried out by means of a computing unit (400) implemented correlation.

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