Tow bar arrangement for control of a self-propelled trailer

A tow bar arrangement for interconnection of a vehicle and a trailer for pulling the trailer by the vehicle,

• wherein the tow bar arrangement comprises a control device in turn comprising a force sensor arranged to sense an instantaneous pulling or pushing force with respect to the vehicle in relation to the trailer,
• wherein the control device is arranged to read said instantaneous force from said force sensor and to produce a control signal for an electric motor arranged to propel the trailer so that a force developed by said motor counteracts said measured force,
• wherein the control device is arranged to measure said measured force to produce a first time series, of force measurement values,
• wherein the control device comprises a low-pass filter arranged to filter a force time series produced based on said first time series as well as upon a desired force value Fd to produce a second time series, of low-pass filtered force measurement values, said low-pass filter being a FIR (Finite Impulse Response) filter designed with a cut-off frequency being between 25% and 75% horizontal resonance frequency of a system comprising the trailer, the tow bar arrangement and an interconnected vehicle, the control device truncating the first time series so that the FIR filter only uses between 1-10 s and/or at the most 200 samples of said first time series, the FIR filter furthermore being time shifted at least 50% of this truncation,
• and wherein the control device furthermore comprises a digital PI or PID regulator, arranged to produce said control signal based on said second time series.